Fall and Winter Vegetable Growing, Harvest and Storage

 

China Rose Winter Radish.
Photo Seed Savers Exchange

You can find a wealth of information on my website about growing, harvesting and storing winter vegetables. There are many links here in this post (all should open in a new tab, so you won’t go down a rabbit hole), and you can also use the search box in the upper right to enter whatever vegetable you are wondering about, and “grow” “harvest” or “store”, Remember I also have several annual series of posts, on Asian greens, root vegetables, workhorse crops, alliums, cooking greens, and lettuce. Just don’t look for “Storage lettuce” until April 1st.

I’ve also included some good blogs that I sometimes consult.

  1. Fall and Winter Vegetable Growing

Season extension into cold weather

Prepare your garden for colder weather: plant winter crops if there is still time, use rowcover on hoops to protect crops from wind and cold weather, plant up every little bit of space in your greenhouse or hoophouse.

See my posts

Spinach over-wintered in our cold frame
Photo wren Vile

And here’s a post by Shannon Cowan, the blog editor at Eartheasy.com:

Winter Gardening: Best Crops to Extend Your Harvest

Shannon suggests using a variety of strategies. “Plant some vegetables that will mature quickly, others that will hold well in your garden beds, and still others that will overwinter and begin growing again when the days lengthen.”

This is also my approach. See my posts

Fall-grown senposai.
Photo Pam Dawling

Good late season vegetables: salad greens, Swiss chard, beans, peas (in climates milder than 7), carrots, radishes, senposai, spinach, pak choy, cabbage and winter lettuces.

Good cold hardy vegetables: Plant in late summer and fall to harvest throughout the winter. These late-sown crops reach full maturity before seriously cold weather, and hold so you can harvest them when the rest of your crops have been eaten. They don’t usually grow much during the winter, but they do stay fresh. Grow enough to supply your needs without depending on any further growth. This category includes Asian greens, beets, broccoli, Brussels sprouts, cabbage, carrots, collards, kale, leeks, scallions, spinach, turnips and other root vegetables,

Good crop protection so you can grow some crops through the winter. If your winter temperatures routinely drop below 25 F (- 4 C), crops need protection, from simple rowcover to hoophouses or greenhouses. This improves the temperatures, but it’s hard to address the reduced amount of daylight or sunlight. The increased warmth, plus the protection from winds, can be enough for some, such as spinach, kale and lettuce, to make some growth whenever their temperature is greater than 40F (5C).

Using a sturdy digging fork to harvest leeks in December.
Photo Pam Dawling

Good slow growing crops to harvest outdoors in late winter or early spring. In this category are crops that go into the winter less than fully grown. After the winter solstice, when the days begin to lengthen, crops start growing again, making them usually ready for harvest very early, much earlier than any crops planted after the solstice. They don’t usually need winter protection and include beets, some types of broccoli, cabbage, carrots, collards, kale, onions, garlic, garlic scallions, spinach, kale and collards.

See my post Winter radishes, planting garlic.

Good crops to grow in hoophouses include arugula, beets, chard, Chinese cabbage, collards, kale, lettuce, Maruba Santoh, mizuna, mustards, pak choy, parsley, radishes, spinach, tatsoi, Tokyo bekana, turnips and Yukina Savoy

Hoophouse Bright Lights chard in winter.
Photo Wren Vile

See my posts

  1. Fall and Winter Vegetable Harvest

See my posts

Harvested Purple Top Milan and White Egg turnips.
Photo Pam Dawling

Here are some links to a couple of good sources for more harvest information:

Piedmont Master Gardeners Garden Shed Newsletter

Guidelines for Harvesting Vegetables by Pat Chadwick

A list of seven basic principles of harvesting, followed by a crop-by-crop list of almost 50 individual crops and a resource list of 18 publications (focused on the mid-Atlantic and Southeast)

Roxbury Farm Harvest Manual (Roxbury Agriculture Institute at Philia Farm)

October Tips from Harvest to Table, by Steve Albert covers all climate zones and comes complete with a USDA Hardiness Zone Map

Links to other posts by Steve Albert

  1. Fall and Winter Vegetable Storage

I already have posts on root cellar potato storage, onion storage (alliums for August), Garlic storage, Storage vegetables slide show, Root Crops April, Feb, Jan, Dec, Nov.

See my posts

Sweet potatoes in storage. An ideal crop for winter meals, as they store at room temperature for a long time, maybe seven or eight months. Photo Pam Dawling

Lettuce All Year in a Changing Climate

Lettuce bed in May.
Photo Wren Vile

We like to eat lettuce year round, and have put time and energy into finding the varieties and planting dates that work best here in Central Virginia, as well as how to get the best results in each season. Recently I revised our lettuce schedules, partly to take account of hotter weather arriving earlier in the year, and also to even out the harvest dates.

I have frequently written blogposts about growing lettuce. And I have a whole year of Lettuce for the Month posts. See here for the overview, or click on the month you want to know more about. These posts are mainly about our favorite varieties for each time of year.

I have a slideshow Lettuce year round  – It’s at the end of this post.

Back in 2006, I wrote Lettuce: Organic Production in Virginia for VABF. We’re now in Winter Hardiness Zone 7a. Back then we were 6b. Read this publication for details you are hazy on, but see our updated Lettuce Varieties List and Lettuce Log in this post.

Fast-growing Red Salad Bowl lettuce.
Photo Bridget Aleshire

Choose appropriate lettuce varieties for each time of year.

Sow several varieties each time to spread the harvest season and the risks of poor germination. I like to use something fast, something slow; at least one red; a romaine, a bibb and a couple of leaf types.

Consider multileaf lettuces too, Salanova and Eazyleaf brands. They are bred for uniformly small leaves, with more texture, loft and flavor than baby mixes and faster harvesting. Transplanted 6″–8″ (15-20 cm) apart they produce 40% more than baby leaf mixes. The full-size plant can be harvested as a head, providing a collection of bite-sized leaves.  Or just one side (or the outer leaves) of the plant can be cut and the plant will regrow for future harvests. Growing multileaf heads takes 55 days, compared to 30 days for baby lettuce

Red Hawk Farm hoophouse densely planted with multileaf lettuces.
Photo Pam Dawling

Our recent changes to our Lettuce Varieties List include switching over from “Early Spring” varieties to “Spring” varieties at the end of February rather than the end of March. This means we only make 3 sowings of the early spring varieties, and we need to stop buying much seed of those varieties! Next year I might even abolish that category and those early varieties to simplify life.

The spring varieties we now sow from February 28 to April 22. We used to sow these until May 15. We’re still making 5 sowings of those, but the dates have moved earlier.

On April 23 we switch over to our Summer varieties, which we make 20 sowings of, until August 14. (Buy lots of seed of those varieties!) We then switch to nine sowings of Fall varieties, until September 7.

Lettuce growing in our greenhouse in November.
Photo Wren Vile

From September 8 to the end of September we use our cold hardy varieties. These 9 sowings include those for the greenhouse and hoophouse, which will feed us all winter. 

Click to access Lettuce-Varieties-pdf.pdf

You’ll need a large screen, a magnifying glass or the ability to expand the image.

We like to grow a balance of leaf lettuce and head lettuces, and, in winter, baby lettuce mix too. We harvest the baby lettuce mix when 3″–4″ (7.5–10 cm) tall, cutting 1” (2.5 cm) above the soil. We harvest leaves from the big lettuces the rest of the time. Baby lettuce mix is very pretty, but I actually prefer the juiciness and crunch of big lettuce.

Beautiful baby lettuce mix in our hoophouse.
photo Wren Vile

Keys to year round lettuce

  • ·         Store seed in a cool, dry, dark, mouse proof place.
  • ·         Grow your lettuce quickly, for high quality and flavor, using good soil preparation and high organic matter.
  • ·         Learn the skills of lettuce germination in all weathers. Minimum soil temperature for germination is 35°F (1.6°C).  Optimum temperature range for germination is 68°F–80°F (20°C–27°C).1/4″–1/2″ (6–10 mm) deep is ideal.  Good light.
  • Watch the temperature – Germination takes 15 days at 41°F (5°C), 7 days at 50°F (10°C), 3 days at 68°F (20°C) and only 2 days at 77°F (25°C). Germination will not occur reliably at temperatures hotter than 86°F (30°C).
  • Keep watching the temperature –  Optimum growing temperatures are 60°F–65°F (15°C–18°C), Some growth occurs whenever the temperature tops 40°F (4.5°C).
  • ·         Choose good locations! We grow lettuce outside from transplants from February to December (harvesting from late April); in a solar-heated greenhouse from September to March (harvesting leaves from November) and in a solar heated hoophouse from October to April (harvesting leaves from November, and whole heads in April). We also sow baby lettuce mix in the hoophouse from October to February, for harvest multiple times from December to April.
  • ·         Use shade cloth on hoops in hot weather
  • ·         Use rowcover in cold weather, or plant in cold frames, greenhouses or hoophouses.

Lettuce under shade cloth.
Photo by Nina Gentle

Grow a consistent lettuce supply using succession crop planting

To have a continuous supply, it is important to plant frequently, at intervals adapted for the time of year. The gap between one sowing and the next gets smaller as the year progresses; the gap between one transplanting and the next does likewise. The number of days to reach transplant size dips to 21 days in the summer, then lengthens as the weather cools and the days get shorter.

We made a Lettuce Succession Crops graph using our records for sowing date and harvest start date. From this we determined the sowing dates to provide us with a fresh harvest (120 heads of lettuce, or equivalent) every single week. We made a Lettuce Log with our planned sowing, transplanting and harvest dates. This is explained in my slideshow Lettuce year round.

Lettuce Succession Crops Graph

Click to access Lettuce-Succession-Crops.pdf

Rouge d’Hiver hardy romaine lettuce.
Photo Bridget Aleshire

Recently I fine-tuned this in light of more recent records. In some cases we had been led astray by a spreadsheet date calculator that was based on 30 day months in a 360 day year! Not reality! We also had data showing that transplants were not always ready on the dates we had thought, probably due to a mistake in an earlier year when we were unable to transplant on time, and repeated the delayed date the next year. Most of the tweaking was in early and late spring, and then in August.

Click to access Lettuce-Log.pdf

Tips for growing good quality lettuce

I recommend transplanting lettuce (other than baby lettuce mix) at 4-6 true leaves (3-6 weeks of age). It is worth learning good transplanting skills, so that plants thrive, even if transplanted in mid-summer.

Water enough, with an efficient irrigation system. Water new transplants daily for the first 3 days, then every 4-7 days after that. Lettuce needs a relatively large amount of water throughout its growth.  Deeper weekly waterings equivalent to 1” (25 mm) of rain are better than frequent superficial irrigation – roots will grow deeper, giving the plant greater drought-resistance.

To make best use of space and time, plant lettuces 10-12” (25-30 cm) apart, in a hexagonal pattern. If you plant too close, you are restricting the size of the lettuce. If you plant with more space than needed, you will waste time dealing with more weeds!

Flats of lettuce transplants in our cold frame in April.
Photo Pam Dawling

Transplanting gets a head start on weed control, which is important from planting to a couple of weeks before harvest. Don’t waste time hoeing lettuce you will be harvesting next week. I generally find that if I hoe once, a couple of weeks after transplanting, that is all the weed control I need at the fast-growing time of year. We like the stirrup, or scuffle, hoes, which are safer in the hands of novices than sharp edged hoes, because the blade is in a closed loop.

Some growers use black plastic mulch, but I hate filling the world with single use plastic, so we don’t do that. Some others use landscape fabric with melted holes at the right spacing. I used this for strawberries and liked it. I’m not sure I’d find it worthwhile for fast-growing lettuce. No-till growers can transplant into mulch, first making what we call “nests” at the appropriate measured spacing. It’s tempting to skip the measuring, but if you drift from a 12” (30 cm) spacing to a 15” (38 cm) spacing, you will end up with fewer lettuces!

For those who like to direct sow lettuce, you could prepare the bed, let it rest for a week (watering it), then flame or lightly hoe the surface before sowing to remove a flush of weeds.

Lettuce seedlings for transplanting later. Photo Pam Dawling

Bolting and/or bitterness are more likely with under-watering, long days, mature plants, poor soil, crowding, high temperatures, and vernalization—once the stems are thicker than 1/4″ (6 mm), if plants suffer 2 weeks of temperatures below 50°F (10°C), followed by a rapid warm-up.

Bolting lettuce in July
Photo Alexis Yamashita

Deal promptly with pests and diseases. Aphids, cutworms, slugs, rabbits, groundhogs and deer all like lettuce as much as we do. If you find your lettuces melting down with fungal diseases, you can, of course, commit to better crop rotation. You can also consider solarizing beds for next year’s lettuce. You need a minimum of 6 hot weeks in which to cook the soil-borne disease spores by covering the prepared beds tightly with clear plastic. Old hoophouse plastic is ideal – construction plastic does not have the UV inhibitors that prevent the plastic shattering into shards. 

More resources

Cornell has a 2016 Organic Production and IPM Guide for Lettuce 67 pages of everything you are likely to need, for growing in New York type climates, at least.

Ray Tyler at Rose Creek farm has a Lettuce Masterclass, a step-by-step blueprint to plan, grow, and sell lettuce year-round!

This slideshow is from 2019, before I made the changes I mention above.

Lettuce Year Round 60 mins

Planning Winter Cover Crops

 

A cover crop mix of winter rye, hairy vetch, Austrian winter peas and crimson clover.
Photo Bridget Aleshire

If you haven’t already made a plan for winter cover crops, this is a good time to do it. Having plants growing through the winter, or at least into the winter until they get killed by cold temperatures, will improve your soil both physically (the roots hold the soil in place, preventing erosion, and they open up channels that improve the drainage) and biologically (the soil microorganisms thrive when they have active plants to cooperate with, exchanging nutrients). Cover crops will also reduce the number of weeds you have next year, because they crowd out weed seedlings. In some cases they even inhibit weed seeds from germinating.

I have some slideshows about cover crops, and am including one at the end of this post.

Choosing the “perfect” cover crops can be confusing, but any is better than none, so I encourage you to experiment and keep records, so you can improve your choices each year. It helps to know your first frost date, and your winter-hardiness zone (the lowest temperature your garden is likely to encounter). A two-week delay in sowing can seriously reduce the effectiveness of the cover crop, so follow these guidelines if you can.

A cover crop of overwintered oats the year they didn’t die.
Photo Pam Dawling

Short Simple Guide to Winter Cover Crops

  1. If the area has been fully harvested of food crops by 60-80 days before frost, sow a frost-killed cover crop or even a fast-growing food crop. Buckwheat, soy, cowpeas, spring peas, sunnhemp, Japanese millet, sorghum-sudangrass will frost-kill. Forage radish lab-lab bean or bell beans will die back and leave almost bare soil. Don’t sow a winter cover crop yet. If sown too early, oats head up in the fall and even drop seed.
  2. If the area is clear of vegetable crops by 40-60 days before frost, sow oats to winter-kill. If possible add a legume (soy and spring peas are easy, and will be killed by the frost, so they won’t complicate food crops next year). For us with a first frost date of October 14, the cut-off date for oats is September 7. This would be after growing early sweet corn, spring broccoli, cabbage, spring-planted potatoes or early season spinach, lettuce, beets, carrots. Oats will winterkill completely at 6°F (-17°C) or even milder than that, leaving the plot quick to prepare for early crops next year. So plan to put your early crops where you had oats in the winter. See the slideshow for more about oats.

    Crimson clover cover crop in flower.
    Photo McCune Porter
  3. If the area is ready for cover crops 20-40 days before frost, sow winter wheat. Add a legume such as crimson clover, if you won’t need to prepare the area before it flowers (in central Virginia 4/16-5/2, most usually around 4/20). You get the most nitrogen from the legumes if they reach the flowering stage before you kill them off in spring. If you have a legume that doesn’t reach flowering, it’s not the end of the world, you just get less nitrogen for your money. It is too late to usefully sow cover crops that are not frost-hardy, or even oats, which won’t make enough growth before getting killed.

    Cover crop of winter rye, hairy vetch and crimson clover.
    Photo Kathryn Simmons
  4. If the area is ready for cover crops up to 10 days past the frost date, sow winter wheat or winter rye and hairy vetch or Austrian winter peas. Winter rye is hardier than any other cover crop and can take later planting dates. But it is a bit harder than wheat to incorporate in the spring. Austrian winter peas can be sown later than other legumes.
  5. If you are up to 3-4 weeks past your average frost date, (we choose November 7 here, where our average first frost is October 14), sow winter rye alone. It’s too late for any legumes.

    Cover crop of winter rye still small in March, but holding the soil together.
    Photo Pam Dawling
  6. If you are later than 3-4 weeks past your average first frost date, leave the weeds or crop remains growing. It’s too late to sow a cover crop, and you’ll do more harm than good tilling up the soil. You can mow the weeds anytime you see lots of flowers and seed heads. The weed roots will hold the soil together and help feed the soil microorganisms until early spring. Be prepared to act soon in spring, so you don’t get weed seeds.
Quick Guide to Winter Cover Crops.
Pam Dawling

More Options for Each of These Time-frames

  1. 60-80 days before frost: You could follow a frost-tender cover crop with an over-wintering cover crop, for best effect. If you leave the dead tender cover crops in place, in early spring the winter weeds will start growing in the open space, so be ready for fast action. For the very earliest spring crops, forage radish lab-lab bean or bell beans will die back and leave almost bare soil. While still growing, they suppress weeds. BUT fast-maturing spring vegetables will not do well with no-till cover crops unless you add N fertilizer, as they need nitrogen more quickly than can be got from no-till.
  2. 40-60 days before frost: Austrian winter peas, crimson clover, or red clover are other options for legumes, but they won’t die when the oats do. They are relatively easy to incorporate in spring. Frost-killed cover crops can also be combined with oats. Or for a cover crop to survive the winter, sow winter barley or winter wheat with Austrian winter peas, crimson clover, hairy vetch, red clover, fava beans. Hairy vetch takes a few weeks longer than crimson clover to reach flowering. Which you choose will depend what you want to grow there next spring and when you need to plant it. After oats or other winter-killed cover crop, we like to plant our early spring food crops, peas, cabbage, broccoli, carrots, March-planted potatoes, spinach and the first sweet corn.

    Cover crop height and thickness in late April.
    Photo Kathryn Simmons
  3. 20-40 days before frost: Winter rye, or winter barley are also options for the cereal grain part of the mix, if you have those seeds on hand. In central Virginia, it’s a mistake to sow rye as early as August, as it can set seed. Austrian winter peas, or red clover are other legume options if that’s what you have. Sometimes it pays to use what you already have, as it may not give good germination if saved over to next fall. Winter rye needs 3-4 weeks after tilling in, in spring, to break down and to disarm the allelopathic compounds that stop small seeds germinating. Plan for the next food crops to be ones planted after late April, such as late corn plantings, winter squash, transplanted watermelon, tomatoes, peppers, sweet potatoes, June-planted potatoes, fall brassicas, and second plantings of summer squash, cucumbers, beans.
  4. Up to 10 days past the frost date: it’s too late for clovers. Austrian winter peas winter-kill in zone 6, but are hardy in zone 7. Hardy to 0°F (-18°C). AWP bloom in late April at Twin Oaks, before hairy vetch. Suitable crops in the year before using Austrian winter peas are the late-finishing winter squash, melons, sweet potatoes, tomatoes, peppers, middle sweet corn, June-planted potatoes. The same group of crops are suitable for following AWP, as they are planted after May 1. You can sow AWP several weeks later than clovers, but at least 35 days before first hard freeze (25°F/-4°C) – in zone 7, 8/10–10/24 (11/8 is sometimes OK)

    Winter rye headed up. Mow or turn it under very soon! Don’t let it shed seed.
    Photo Pam Dawling
  5. Up to 3-4 weeks past your average frost date: no really, it’s too late for any other cover crop. If you don’t have winter rye, don’t till! Leave the weeds, see below.
  6. Later than 3-4 weeks past your average first frost date: no, really, do not till! You could mow and tarp, to kill the weeds before spring. I’m not sure what the soil life thinks about that, though! You could mow again in early spring, or till and sow oats, if you won’t be planting a food crop in the following 8 weeks, giving the oats time to make respectable growth before turning them under.

Create a crop rotation for vegetables that includes good cover crops

If you include winter cover crops when planning a crop rotation for your vegetables, you can tweak your plan to maximize your cover crop opportunities. Here’s the steps:

 Figure out how much area is needed for each major crop (the ones needing the largest amount of space).

  1. Measure and map the space available
  2. Divide into equal plots big enough for your major crops
  3. Group compatible crops together to fill out each plot
  4. Set a good sequence, maximizing cover crop opportunities
  5. Include best possible cover crops at every opportunity
  6. Try it for one year, then make improvements

For more details, see my slideshow Crop Rotations for Vegetables and Cover Crops on SlideShare.net

Advanced Options for Winter Cover Crops

Sweet corn with undersown soybean cover crop. Photo Kathryn Simmons

Undersowing

Sometimes you can undersow the cover crop between the rows of a growing food crop, to take over after the food crop dies of frost or mowing. We do this with our last planting of sweet corn, and with fall broccoli and cabbage.

Timing is critical: Sow the cover crop late enough to minimize competition with the food crop, but early enough so it gets enough light to grow enough to endure foot traffic when the food crop is harvested. The leaf canopy of the food crop should not yet be closed. Often the best time is at the last cultivation, often about a month after planting the food crop. With vining food crops, it’s important to sow the cover crop before the vines run.

Choose vigorous food crops, but cover crops that are only moderately vigorous. Ensure the seedbed is clean and the soil crumbs small enough. Use a high seeding rate, whether broadcasting or drilling, and irrigate sufficiently.

A no-till cover crop mix of winter rye, hairy vetch, Austrian winter peas and clover.
Photo Bridget Aleshire

No-till Winter Cover Crops

In the spring, kill the cover crop without tilling it in, and plant food crops into the dying residue. There are three ways to kill cover crops without herbicides:

  1. Winter-killed cover crops for early spring food crops
  2. Mow-killed cover crops.
  3. Roll-killing (but it usually requires special equipment).

We have had one year in 10 as a no-till year. We use no-till cover crops before Roma paste tomatoes, which are transplanted in early May. We don’t need early-ripening for these, making them a good no-till food crop. The soil under no-till cover crops stays colder than tilled soil, slowing the plant growth down.

Late-spring transplanted crops such as late tomatoes, peppers, eggplant, Halloween pumpkins, or successions of cucumbers and squash can do very well after a winter-hardy legume-grass mix no-till cover crop.

To be an effective mulch, you need to get a thick sturdy stand of cover crops, which means sowing in plenty of time, and being generous with the seed. To make the timing work, you need a previous food crop that finishes before the sowing date 4-5 weeks before the average frost (that’s September 7-14 for us).

Timing is also critical in the spring. For maximum N, the legumes in the mix will be flowering right when you need to plant the food crop. Mow the cover crop mix close to the ground, and plant right into the stubble. Transplants or big seeded crops work well. The ground will be relatively hard – you probably can’t make a furrow for small seeds).

It’s not all over with the weed-prevention after that. In our humid climate the no-till mulch biodegrades after 6-10 weeks. In July we roll hay between the rows, to top up the mulch.

Cover Crops for Vegetable Growers 2019 60 mins

Workhorse Crops for June

Farao early cabbage
Photo Pam Dawling

Workhorse Crops for June

I’ve chosen 14 Workhorse Crops (including two pairs) to focus on at the beginning of every month, until April 2022: These are crops that we can rely on under a wide range of conditions. Some Workhorse Crops are easy to grow, some pump out lots of food, some are “insurance crops”, some are especially profitable (for those growing for market), and watermelons are the circus pony among the workhorses, I admit, but we all need fun!

I intend for this series to help growers who want to become more efficient, productive and profitable (if selling) as we emerge from sheltering at home and expand our lives again. Don’t give up growing your own food, just choose some less time-consuming ways to do it.

Our May 5 sowing of bush beans on June 30.
Photo Pam Dawling

Workhorse Crops to Plant in June

June is another busy planting month here in central Virginia. Next month the heat strikes hard, and the daylight starts to get shorter, but this month we are still climbing the hill of the year. Ten of our 14 Workhorse Crops can be planted in June.

Beans: We sow bush beans every few weeks to keep up supplies of tender beautiful beans. See the Special Topic section for info about Succession Planting, to help you determine when and how often to sow beans and other short-lived warm weather crops. Also see the Special Topic section to read how we control Mexican Bean Beetles that used to destroy our bean plantings. Click this link to read about soaking bean seed, using inoculant, sowing through biodegradable plastic mulch using a jig, sowing sunflowers in our bean rows as place-markers when harvesting.

Carrots: I wrote a lot about carrots in the past year, when the monthly series was on root crops. See this post on preparing beds for sowing carrots, and weeding and thinning. Check out this post on flame-weeding, if you plan lots of carrot-growing!

We sow carrots in late February, then twice in March, once a month in April and May and after that we’d like to not sow more until the beginning of August. Carrots grown in hot weather don’t taste that good: there’s little sweetness and too many terpenes (the compound that in small quantities gives carrots their distinctive carrotiness, but can be overpowering if too strong.) But home-grown hot weather carrots are still better than jet-lagged travel-weary carrots from afar. You could use shadecloth over the beds. If we have not grown enough carrots by the end of May to see us through to October, we sow in June, and even July if we must.

Carrots under shade cloth in summer.
Photo Pam Dawling

Chard: The perfect insurance crop! We use chard for fresh greens in summer, when spring kale, collards, broccoli and cabbage have long bolted and been turned under so we can plant something else. We transplant our chard into a hay mulch in late April. Organic mulches help keep the soil cool during hot weather, so are very helpful for leafy greens. This crop will be in the ground until mid-winter, and mulch will keep back most of the weeds.

Chard provides leafy greens all summer whenever you need them, and you can ignore it when you have plenty of other vegetables! As a biennial, chard will not bolt the first year (unless stressed by lack of water).  I’ve noticed the red chards bolt more easily than the green ones. I suppose red crops are a bit stressed already, as they are short of chlorophyll, compared to the green ones, making photosynthesis harder work.

Potatoes: I wrote a special series on potatoes last year. Click the link to access the whole series, starting with planting in April. Here we plant in March and June. For our June-planted potatoes, we pre-sprout the seed potatoes for just two weeks (shoots grow quicker in warm weather than in early spring). To protect the planted potatoes from the summer heat, we hill immediately after planting, even though we can’t see the rows! Then we unroll big round hay bales down the field to cover all the soil. Potato shoots grow strongly, and can make it up through the extra height of the hills/ridges and through the 3” (7.5 cm) of hay. After about 16 days, we walk through the field, investigating spots where there is no sprout. We call this task “Liberating the Trapped Shoots”. Often the problem is just an overthick clump of mulch, and the shoot will be quite literally trapped (and completely white). We simply let he shoot see the light, and redistribute the over-thick mulch.

June-planted potato emerged through hay mulch.
Photo Pam Dawling

Sweet corn: we make 6 sowings of sweet corn, to harvest from July 4 to mid-October. We are well into corn-planting time, which continues until mid-July, when there are not enough warm days left in the season to mature another sowing. Remember: don’t plant a mixture of different corn genotypes, and don’t plant Indian corn, popcorn or any kind of flint or dent corn within 600′ (180 m) of your sweet corn.  This leads to very disappointing starchy corn. We grow only sweet corn in our garden, to avoid this problem.

Sweet potatoes: I wrote a lot about planting sweet potatoes in 2020. Wait for the soil to warm before planting out your sweet potato slips, they don’t grow well if too cold. We plant ours a couple of weeks after the last frost, around the time we transplant peppers and okra. In early June, we replace any casualties, if needed, to fill out the rows again. This year we have a beautiful looking patch, with rows of healthy plants on ridges, with biodegradable plastic mulch. We have a solar-powered electric fence to deter the deer. My latest worry is groundhogs, who can slip right under the electric fence. They haven’t yet, but I expect they will, if we don’t catch them first.

Sweet potatoes on biodegradable plastic mulch, with solar electric fence charger.
Photo Pam Dawling

Tomatoes: In mid-June we plant a bed of late tomatoes, to boost the yields when the maincrop beds start to pass their peak. We planted our main crop tomato beds at the very beginning of May, and they’re looking quite good.

Here’s a post about planting tomatoes in our hoophouse. We use the same techniques in the hoophouse and outdoors. We transplant one row of tomatoes down the centerline of a 4ft (1.2 m) bed, 2ft (60 cm) apart. Once the weather has settled so that we’re confident we won’t need rowcover any more, we stake and stringweave. We install a steel T-post every two plants (4ft /1.2 m) apart and start stringweaving when the plants are about 12ins (30 cm) tall. I’ll say more about stringweaving next month.

Watermelons: As I explained in May, I gave watermelon a “Circus Pony” place among the workhorses! They’re not easy, therefore not reliable, but they provide so much pleasure when they do grow well. We transplant our watermelons, to get ripe ones as early as possible.

Watermelons grow very well on black plastic mulch, which warms the soil as well as keeping weeds at bay. The first year we switched from using hay mulch to biodegradable plastic mulch, we were astounded to get ripe melons a full month earlier!

If you want to use organic mulches for warm weather crops, don’t do it immediately. Wait till the soil warms through. This year we made that mistake, then we had late cold weather and the transplants all died. We’re going to experiment with station-sowing seeds directly in the gaps. Station-sowing is a technique of putting several seeds in the ground at each spot (station) where you want one plant to grow. Rather than making a furrow and sowing a row that needs thinning later. It’s a good technique for remedial work (ahem!), or if growing very expensive seeds, or for crops you are not familiar with, such as parsnips. You see several seedlings all the same and can be pretty sure it’s the thing you planted.

Watermelons can be planted from seeds when the ground has warmed to at least 70°F (21°C). On average, it takes about 85 days for Crimson Sweet seedlings to mature and produce ripe fruit. This is late for us to sow watermelons, and we certainly won’t get early ones this year, but we could get them in September. Better than none.

I described transplanting watermelons last month, if you need that info.

Crimson Sweet watermelon.
Photo Nina Gentle

Winter squash are a true workhorse, and can still be sown here early in June, provided we don’t sow the slow-maturing ones like the gigantic Tahitian Butternut. Aim for harvesting in September and October and count back to see how many days you have until you want to harvest. Then choose the varieties that will have enough time. You can also transplant winter squash if you need to. We did this once when our fields flooded. It worked out fine.

We mostly grow Butternuts, Moschata types that store best. This is the type to focus on if you want squash with no damage from borers or cucumber beetles. The tougher stems are better able to repel invaders. They need warm growing temperatures above 60°F (16°C).

See last month’s post for more about sowing winter squash, and for other kinds of winter squash, such as some Maxima squashes that store quite well and have relatively high resistance to squash bugs compared to others in this group, and Pepo squashes, suitable for storing a few weeks only

A bee pollinating squash.
Photo Pam Dawling

Zucchini (courgettes) and summer squash: another crop type that we succession sow, to get a continuous supply. More about succession planting below in the Special Topic section. We make five or six plantings, each one half yellow squash (Zephyr, Gentry) and half zucchini (TenderGrey, Noche, Golden Glory). We grow our earliest squash in the hoophouse, setting out transplants at the beginning of April. Our first outdoor crop is also from transplants. After that, the soil is warm (60°F/15.5°C) and we direct sow. The time from sowing to harvest is only around 42-54 days.

After transplanting or sowing, we hoop and cover the row with insect netting (rowcover works if it has no big holes). We have many bugs that like these plants, especially the striped cucumber beetles, so we keep the rows covered until female flowers appear. At that point we need the service of the pollinators, unless the squash is parthenocarpic (sets fruit without pollination). We pack away the covers, hoe and thin the squash to 24” (60 cm). It would be better to thin sooner, but we rarely find the time.

Workhorse Crops to Harvest in June

We have mnemonics for harvesting: Monday, Wednesday and Friday might be the crops beginning with the plosive Ps and Bs: peas, beans, beets, broccoli, blueberries etc. Tuesdays, Thursdays and Saturdays would be the crops beginning with the hard K and G sounds: kale, corn, carrots, collards, cabbage, garlic scapes etc.

Other crops like asparagus, lettuce, cucumbers, summer squash and zucchini we harvest 6 days a week. Some, like cabbage, we harvest twice a week.

Asparagus can be harvested here until early in June. Every day for the 8-week harvest period, snap off at ground level all the spears above a certain length. We chose 7” (18 cm). This task is best done first thing in the morning, when the spears are crisp. Daily harvest will also remove asparagus beetle eggs, controlling the pest level.

Cabbage is ready here from late May until mid-July. We store enough to feed us until we start harvesting fall cabbage.  An early sowing of fast-maturing varieties (like Farao or Early Jersey Wakefield which can be ready in only 60 days) can be followed by harvests of slower varieties. When a cabbage is ready for harvest, the head is firm and the outer leaf on the head (not the more horizontal wrapper leaves) will be curling back. For cabbage to store to eat over the summer, cut with a strong knife and set it upside down on the nest of leaves to dry a little. Come back along the row with a net or plastic bag and gather up the storage quality cabbages to refrigerate. Gather any lower quality cabbages to eat soon. If you would like to get another harvest from the same plants, cut criss-cross into the stump. Small “cabbagettes” will grow and can be used raw or cooked. They won’t store.

Carrots can be ready about three months after sowing in spring, although you can get thinnings for salads sooner. Read here about harvesting carrots.

Chard is ready for harvest as soon as you decide the leaves are big enough. Simply snap or cut off some outer leaves and stand them in a bucket with a little water until you cook them. For a sustainable rate of harvesting with chard, always leave at least 6 of the inner leaves to grow.

Garlic harvest time will be soon if not already. I wrote about garlic last week.

Kale and collards can be harvested until they are bolting, as long as the flavor is acceptable. Our spring-planted ones are not bolting yet, but the fall-planted ones were tilled in a couple of weeks ago.

New potatoes could be dug here during June, if you don’t mind reducing the final yield. The flavor of new potatoes, with their delicate skins, is very special. As a child, I ate them boiled with mint, and topped with some butter.

Tomatoes start to ripen this month. Our hoophouse tomatoes have started to yield a small amount of Glacier, Stupice, Sungold and Amy’s Apricot.

 

Zucchini harvest.
Photo Brittany Lewis

Zucchini and summer squash are ready from the hoophouse early sowing since about May 20.  We are now (June 2) harvesting our first planting of outdoors. We harvest every day to the fall frost (or beyond if we remember to cover that last planting with rowcover on chilly nights.).

From storage: carrots, potatoes,

 Workhorse Crops Special Topic:

Succession planting, and Mexican bean beetles

Succession planting is a topic I have often presented at workshops, so rather than give you more words, I’m giving you the slideshow from 2019. Towards the end it includes information about dealing with Mexican bean beetles.

 

 

 

Everything You Want to Know About Garlic: Garlic Almanac and Phenotypic Plasticity

Silverwhite Silverskin garlic
Photo Southern Exposure Seed Exchange

Everything You Want to Know About Garlic:

Garlic Almanac and Phenotypic Plasticity

(How garlic adapts to its locality)

It’s garlic harvest season for many of us and I notice many growers are searching my site for information. Here are quick links.

Garlic signs of maturity from October 2020

Everything You Need to Know About Garlic includes all the links listed below here.

Much about garlic is to be found in my Alliums for the Month Series:

Garlic harvest.
Photo Twin Oaks Community
Other posts about garlic, starting with harvest:
Pulling garlic scapes.
Photo Wren Vile

Phenotypic Plasticity

Phenotypic plasticity of garlic refers to the changes to a garlic variety grown in a particular location. Genetically identical garlics can grow differently in different environments. Garlic reproduces asexually, the new cloves are all clones of the mother plant, with no new genetic material introduced. And yet, over time, garlic saved and regrown each year in a certain locality will adapt itself to that location, due to the particular soil type, water availability, local temperatures, latitude, altitude and cultural practices. For example, studies have shown that varieties grown in drought-prone areas can, over years, develop more drought-tolerance. Commercial cultivars can have the highest bulb yield under well-watered conditions, but drought will show up the adapted strains in a comparison trial.

Garlic Plants
Photo credit Kathryn Simmons

We have been growing our own strain of hardneck garlic for over 30 years, and it does really well here. Originally the seed stock was a bag of garlic from the wholesale vegetable market. This is the very thing we are told not to do, as it may introduce pests and diseases. Indeed, it may, but our original folly is now deep in the past, and we have fortunately seen no problem.

I was reminded about phenotypic plasticity, when a friend and neighboring grower reported that the seed garlic we had passed on to her was doing well and was mature a couple of weeks before the variety she normally grows.

From the 2004 work of Gayle Volk et al, Garlic Seed Foundation analyzing 211 garlic accessions, we have learned that there are many fewer genetically distinct varieties of garlic than there are named varieties. Of the 211 accessions in that trial, only 43 had unique genotypes. But garlic shows high biodiversity and ability to adapt to its environment. The same garlic genotypes in different environmental conditions can show different phenotypes. This demonstrates the high phenotypic plasticity of garlic, probably linked to its complicated genetics, which somehow compensate for lack of sexual reproduction.

Work done in 2009 by Gayle Volk and David Stern, Phenotypic Characteristics of Ten Garlic Cultivars Grown at Different North American Locations  addressed the observation that garlic varieties grown under diverse conditions have highly plastic environmental responses, particularly in skin color and yield. This is a very readable paper for non-academic readers. Ten garlic varieties were grown at twelve locations in the United States and Canada for two consecutive years to identify phenotypic traits of garlic that respond to environmental conditions. The purpose of the study was to determine which phenotypic traits are stable and which vary with location.

Inchelium Red softneck garlic – note the small cloves in the center.
Photo Southern Exposure Seed Exchange
  • Clove number, weight and arrangement, clove skin coloration, clove skin tightness and topset number, size and color stay true to variety independent of location.
  •  Mostly, varieties classified as hardneck types produced scapes and those classified as softnecks did not, but there were some exceptions.
  • Bulb size, bulb wrapper color and bulb elemental composition (flavor) are related to location, (the influence of the local environment, such as the weather in that production year and the soil mineral content), rather than variety. The intensity of the skin patterns is highly dependent on the location. Some general trends were noted, but no clear correlation was found. (Read the study for the details).
  • For good size, predictably colored and flavored garlic, buy seed garlic grown locally that yields well. When garlic is grown in similar conditions to those in which it was produced, yields can remain consistent or improve.

    Our softneck garlic in May.
    Photo Pam Dawling
  • Varieties that grow well thousands of miles away are not a guarantee of a good result in your garlic patch. They may not match the bulb size, shape, color and flavor listed in the catalogs.
  • When grown under the same environmental conditions, the leaf number before bolting, flowering date, the final stem length, the flower/topset ratio, and pollen viability vary from one variety to another.
  • Studies that compared bulb firmness, pH, soluble solids, moisture content and sugar content with appearance determined that many of these traits are independent of skin color across 14 garlic varieties.
  • Bulb size was highly dependent on growth location with northern sites producing larger bulbs overall than southern sites for at least half of the trial varieties. Regional differences between varieties with respect to bulb size were noted, but because the project had a limited number of sites, specific variety recommendations for different regions were not provided.
  • Bulb size and weight were positively correlated with soil potassium levels.
  • Bulb sulfur and manganese content (flavor) were correlated with soil sulfur and manganese levels.

    The famous Music garlic, a hardneck type – see the stem.
    Photo Southern Exposure Seed Exchange
  • The demand for high-quality fresh garlic is increasing as restaurants and consumers seek out local vegetables. Consumers are attracted to colorful, unique garlic varieties for different culinary uses. As variety name recognition in garlic increases, understanding which traits define particular varieties and which traits vary within cultivars, depending on environmental conditions, will be valuable for successful marketing of new garlic types.

Workhorse Crops for May

Young bush bean plants.
Photo Pam Dawling

Workhorse Crops for May

Workhorses crops are reliable under a wide range of conditions, including weather, soil, date and other variables. Some are easy to grow, some pump out lots of food, some are “insurance crops” like chard that stand in your garden until you need to harvest them, some are especially profitable (for those growing for market).

I’ve chosen 14 crops (including two pairs) to focus on in the next 12 months, ending April 2022: Asparagus, beans, cabbage, carrots, chard, garlic, kale and collards, potatoes, sweet corn, sweet potatoes, tomatoes, watermelons, winter squash, zucchini and summer squash.

My motivation for this series is to help all who want to be more efficient, productive and profitable (if selling) as other parts of our lives expand again.

Workhorse Crops to Plant in May

May is a busy planting month here in central Virginia and probably most places in the northern hemisphere. Ten of our 14 Workhorse Crops can be planted once frosts are behind us.

Beans: We grow bush beans because we don’t like putting up trellises. In the past we had uncontrolled Mexican Bean Beetles that destroyed slower-to-mature pole beans. We found we could get crops of bush beans faster and sow them every few weeks or so to get a good supply of presentable beans every couple of days. Click this link to read about soaking bean seed, using inoculant, sowing through biodegradable plastic mulch using a jig, sowing sunflowers in our bean rows as place-markers when harvesting. See my phenology post for information on when it’s warm enough to start sowing beans (and other crops) where you are.

Carrots: I wrote a lot about carrots in the past year, when the monthly series was on root crops. See this post on preparing beds for sowing carrots, and weeding and thinning. Check out this post on flame-weeding, if you plan lots of carrot-growing!

Multicolored chard. Wren Vile

Chard: A great insurance crop – it provides leafy greens when you need them, and you can ignore it when you have plenty of other vegetables! As a biennial, chard will not bolt the first year (unless stressed by lack of water). We use chard for fresh greens in summer, when kale, collards, broccoli and cabbage from the spring have long gone. Because we don’t need chard until late May, we don’t sow until late March. We transplant in late April, into a hay mulch. This crop will be in the ground until mid-winter, and mulch will keep back most of the weeds. You could, of course, sow chard earlier if you want to eat it earlier. We also grow chard through the winter in our hoophouse, where it feeds us during the Hungry Gap.

Potatoes: I wrote a special series on potatoes last year. Click the link to access the whole series, starting with planting in April. Here we plant in March and June. You can plant at any date in between, so long as you have 80 days until your first frost. If time is a bit short, choose a fast-maturing variety (or be satisfied with small potatoes that won’t store).

Sweet corn: we make 6 sowings of sweet corn, to harvest from July 4 to mid-October. Start planting sweet corn when the leaves of the white oak are as big as squirrel’s ears. Click the link to check our planting dates, and to read about our first sowing of the year, catching raccoons and skunks, avoiding mixing types of corn and to view my slide show on succession planting. There’s a confusing aspect of hybrid corn varieties: if you plant a mixture of different genotypes, it can lead to starchy unpleasant-flavored corn. Also don’t plant Indian corn, popcorn or any kind of flint or dent corn within 600′ (180 m) of your sweet corn. For this reason we grow only sweet corn in our garden.

Our first sweet corn of the season.
Photo Pam Dawling

Sweet potatoes: I wrote about planting sweet potatoes in 2020. Modern varieties of sweet potatoes grow to a good size in as little as 90 days, so they are not just for the South! The further north you are, the longer the daylight at midsummer and the more photosynthesizing the plants can do. I have known people grow sweet potatoes in hoophouses if their climate isn’t warm enough outdoors. This can fit with winter use of the hoophouse for greens and roots. My book Sustainable Market Farming contains a whole chapter on this crop, including growing your own slips, but it’s too late to start that this year. Wait for the soil to warm before planting out your sweet potato slips. We plant ours a couple of weeks after the last frost, around the time we transplant peppers and okra.

Tomatoes: We plant out our main crop at the very beginning of May, unless the weather is too cold. To my surprise, I find I haven’t written much about transplanting tomatoes outdoors. Here’s a post about planting tomatoes in our hoophouse. We use the same techniques in the hoophouse and outdoors. We transplant one row of tomatoes down the centerline of a 4ft (1.2 m) bed, 2ft (60 cm) apart. Outdoors, once the weather has settled so that we’re confident we won’t need rowcover any more, we stake and stringweave. We install a steel T-post every two plants (4ft /1.2 m) apart and start stringweaving when the plants are about 12ins (30 cm) tall. I’ll say more about stringweaving later in the year.

Watermelon transplants in a Winstrip plug flat. Watermelons give earlier harvests from transplants, and plants in plug flats transplant easier then from open flats.
Photo Pam Dawling

Watermelons: Watermelon growing isn’t easy, but the rewards are so wonderful, that I gave watermelon a “Circus Pony” place among the workhorses! We transplant our watermelons, to get ripe ones as early as possible. Melons are tricky to transplant, as the roots don’t do well if disturbed. We have successfully used soil blocks, and these days we use Winstrip 50-cell trays. Watermelons grow very well on black plastic mulch, which warms the soil as well as keeping weeds at bay. The first year we switched from using hay mulch to biodegradable plastic mulch, we were astounded to get ripe melons a full month earlier!

It’s important to keep the little seedlings in the greenhouse warm and in very good light, and away from drafts. Be careful not to overwater. They can keel over very quickly and once the stem collapses, remove that seedling before others die too. The goal is short stems!

When you transplant, get the start out of the flat and into the ground as quickly as possible with as little root damage as you can manage. This is not a crop where one person plops the plants out down the bed and someone follows planting them! Make the hole in the soil (through the plastic if you’re using that), by wiggling the trowel from side to side. Don’t dig a hole as if you are in a sand box, with a spoil heap at the side. Just form a space the right depth to get the whole of the stem in the ground.

Next gently pop the transplant out of the flat, perhaps using a table knife down the side of the cell. Push up from underneath. If all goes well, you’ll have the plant in a little block of soil (yes, like a soil block). Slide the transplant into the hole. You want all the leaves above ground, all the roots and stem in the ground. If the hole is too deep, lift the transplant carefully and scrape some soil into the hole. You don’t want to end up with the plant in a dip, as this can rot the stem. If the hole is not deep enough, you can to some extent hill up soil around the stem to protect it. You don’t want any of that fragile stem visible!

Water the day before, and one hour before transplanting, to help the soil hold together, and so that the plant has some reserves of water to see it through the initial shock of being set out. As you are transplanting, pause and water newly set plants every 20 minutes or so. Afterwards, water the whole planting and repeat on the 2nd, 3rd, 5th, 7th days and once a week after that.

Winter squash: By contrast, winter squash are very easy, and they store for months at room temperature. A true workhorse. We direct sow at the end of May, with the goal of harvesting in September and October, the last ones making Halloween lanterns. Soil should be at least 60°F (15.5°C), and all danger of frost should be past.

Young squash plant.
Pam Dawling

We have grown about 400ft (120 m) for 100 people, and mostly focus on Butternuts, Moschata types that grow best where we are and store longest. This is the type to focus on if you want trouble-free squash, with no damage from borers or cucumber beetles. The tougher stems are better able to repel invaders. They need warm growing temperatures above 60°F (16°C). As well as Waltham Butternuts, we include the large Cheese pumpkin, the long-storing Seminole, and the gigantic Tahitian Butternut. We also grow a couple of Maxima squashes which store quite well:  Cha-cha kabocha, and the large blue Jarrahdale, which have relatively high resistance to squash bugs compared to others in this group. Red Kuri, Festival (sweet dumpling type) and the New England Pie pumpkin are Pepo squashes, suitable for storing a few weeks only. (Pumpkins are squashes.) We grow some of these because they are sooner to harvest. Really they are more of a fall squash than a winter squash.

Winter squash do need a lot of space for each plant. This can mean a lot of hoeing until the vines spread, or mulch. Some can take 90-120 days to reach maturity, so plan carefully to be sure of getting a harvest. For dryland farming, without irrigation, it is important not to move the vines to new positions: the dew and rain drips from the leaf edges encourage root growth directly below the vines (where they get the most water and shade).

Sow 0.5”-1” (1-2 cm) deep. Either “station sow” 2 or 3 seeds at the desired final spacing, or make a drill and sow seeds 6” (15 cm) apart. There are various stick planters and jab planters that can be used for this kind of station sowing. Thin later. Rows will need to be 6’ (1.8 m) apart, or more. 9’ (2.7 m) between rows for the vining ones. Some growers plant in a square pattern so that spaces between rows can be mechanically cultivated in both directions. Bush varieties take less space than the vining types, and rows can be 4’ (1.2 m) apart.

You can transplant winter squash if you need to. We did this one year after our fields flooded. We started seeds in cell packs a week before our usual sowing date of 5/25. It worked just fine.

Summer squash plants under insect netting.
Pam Dawling

Zucchini (courgettes) and summer squash: Zucchini is a subset of summer squash. These are easy to grow, fast to produce warm weather crops. We make a succession of five or six plantings each year, so that we can harvest every day. Each sowing is half a yellow squash (Zephyr, Gentry) and half a zucchini (TenderGrey, Noche, Golden Glory). We grow our earliest squash in the hoophouse, setting out transplants at the beginning of April. Our first outdoor crop is also from transplants. After that, the soil is warm enough to direct sow – 60°F (15.5°C).

After transplanting or sowing, we hoop and cover the row with insect netting (rowcover also works if it has no big holes). We have many bugs that like these plants, especially the striped cucumber beetles, so we keep the rows covered until female flowers appear. At that point we need the service of the pollinators, unless the squash is parthenocarpic (sets fruit without pollination). At that point we pack away the covers, hoe and thin the squash to 24” (60 cm). it would be better to thin sooner, but we rarely find the time.

Zucchini and summer squash are another crop type that we succession sow, to get a continuous supply. More about succession planting another time. The time from sowing to harvest is only around 50 days.

Workhorse Crops to Harvest in May

Asparagus photo by Kathryn Simmons

Asparagus can be harvested if you have a patch. If not start to prepare a patch to plant out one-year crowns next early spring. Remove all perennial weeds while growing a series of cover crops. If you have asparagus, you probably know to snap off at ground level all the spears above a certain length. We chose 7” (18 cm). Do this every day for the 8-week harvest period. Daily harvest will also remove asparagus beetle eggs, controlling the pest level.

A bed of Early Jersey Wakefield cabbage in mid-May.
Photo Pam Dawling

Cabbage can be ready from late May, if you made an early sowing of fast-maturing varieties. Farao or Early Jersey Wakefield can take only 60 days.

Carrots can be ready from late May, if you sowed some in mid-late February

Chard is ready for harvest from late May (earlier if sown earlier), see above.

Harvesting garlic scapes in May
Photo by Wren Vile

Garlic scapes appear in hardneck garlic plants. Here it is also an indicator that our garlic will be ready to harvest in three weeks.

Kale and collards can be harvested until they are bolting, as long as the flavor is acceptable. Read more about bolting here.

Zucchini and summer squash from mid-May,

From storage: carrots, potatoes, sweet potatoes, winter squash

Workhorse Crops Special Topic: Deciding Which Vegetable Crops to Grow

Here’s a slideshow to help you decide which crops to grow. Some of the points are for commercial growers, some apply to anyone growing vegetable crops.

Deciding Which Vegetable Crops to Grow, Pam Dawling

Preparing to order seeds

Preparing to order seeds: 6 steps + 3 extra tips

Leeks grow slowly. Sow in March to have seedlings this size in May. Order seed soon! Photo Pam Dawling

There are lots of new gardeners now, as a result of the pandemic causing people to stay at home, cook more and want more food security without going inside grocery stores. Maybe last year you bought packets of seeds in a hurry, either online or off a rack in as store. Maybe you hope your garden will go more smoothly this year and I’m here with this blog post to help you.

Or perhaps you are a new professional grower, seeking to improve your game. Or an established one, looking to hang in there by farming smarter in these hard times.

‘Tis the season for garden planning. Inventory your seeds left from last year, peruse the catalogs and prepare your seed orders. The earlier you get them in, the more likely you are to get the varieties you want, before anything is sold out. Be prepared, note your second choice, and fend off disappointment!

Vates kale seedlings for bare-root transplanting.
Photo Pam Dawling

I have a course on garden planning for home gardeners, on the Mother Earth Fair Online. It consists of eight half-hour workshops, covering all aspects of garden planning from clarifying your goals, choosing crops, making maps of what will go where, planning when you want to harvest, determining how long your rows will be and how much seed to order, deciding when to plant and scheduling everything to make the year go smoothly. There are also workshops on ways to pack more in, and how to be prepared for things that don’t go according to plan!

Mother Earth News Fair

Commercial growers and energetic home growers will also be interested in the information on garden planning in my book Sustainable Market Farming.

I have a couple of slideshows on SlideShare.net,

See Crop Planning for Sustainable Vegetable Production 2019 Pam Dawling

To view it full screen, click the diagonal arrow in the lower right.

For long-term soil health and sustainability, think about crop rotations. See Crop rotations for vegetables and cover crops 2014, Pam Dawling

Buckwheat seedlings. Buckwheat is our quickest easiest summer cover crop.
Photo Pam Dawling

 First, a basic 6 steps of garden planning

  1. See How to Decide Which Crops to Grow.

Think about what you grew last year, and whether you want the same again. Think about what you wished you’d grown. Every year we try to introduce a new crop or two, on a small scale, to see if we can add it to our “portfolio.” Some-times we can successfully grow a crop that is said not to thrive in our climate. (Brussels sprouts really don’t). We like to find the varieties of each crop that do best for our conditions. Later we check how the new varieties do compared with our old varieties. We use heirloom varieties if they do well, hybrids if they are what works best for us. We don’t use treated seeds or GMOs, because of the wide damage we believe they do. For ideas of what you might grow, see our Twin Oaks Harvest Calendar by Crop.

Sowing Rainbow Chard. in a Winstrip tray
Photo Pam Dawling

2. Are any of your leftover seeds OK to keep?

See making an inventory, and Ordering seeds! Seed Viability Many seed catalogs include information about seed longevity, and so does Nancy Bubel in The Seed Starters Handbook. Frank Tozer in The Organic Gardeners Handbook has a table including minimum, average, and maximum.

Seeds stored in glass jars
Photo courtesy of Monticello

A simplified version of how long to keep seeds is as follows:

  • Year of purchase only: Parsnips, Parsley, Salsify, and the rarer Sea Kale, Scorzonera
  • 2 years: Corn, Beans and Peas of all kinds, Chives, Dandelion, Martynia, Okra, Onions,
  • 3 years: Asparagus, Carrots, Leeks, Rutabagas, Turnips,
  • 4 years: Artichokes, Basil, Cardoons, Chard, Peppers, Pumpkins, Spinach, Squash, and Watermelons,
  • 5 years: Beets, most Brassicas, Celery, Celeriac, Chicory, Cucumbers, Eggplant, Endive, Lettuce, Muskmelons, Tomatoes,

Rather than deteriorating with age, some very fresh seed has a dormancy that needs to be overcome by chilling (lettuce).

The fuller story is that storage conditions make a big difference. Keep seed cool, dark, dry in airtight, mouseproof containers.

An old hand-drawn map of one of our garden areas.
Image Pam Dawling
  1. How Much of What to Grow?

Make a rough map of your garden space and see what will fit. Remember you can plant a later crop in the same space after an earlier one finishes. See below for more info on quantities of potatoes and garlic, two staples.

  • How Much Garlic to Plant

A yield ratio of 1:6 or 7 seems typical, and makes complete sense when you consider you are planting one clove to get a bulb of 6–7 cloves. Divide the amount you intend to produce by six to figure out how much to plant. For large areas 750–1,000 lbs/ac (842–1,122 kg/ha) are needed for plantings in double rows, 3″–4″ in-row (7.5–10 cm), beds 39″ (1 m) apart. For single rows, 8 lbs (3.6 kg) of hardneck or 4 lbs (1.8 kg) of softneck plants about 100′ (30 m). In the US, one person eats 3–9 lbs (1.4–4.2 kg) per year.

Music hardneck garlic.
Photo Southern Exposure Seed Exchange
A row of potato seed pieces ready to cover.
Photo by Wren Vile
  1. How Much Seed to Order?

Hopefully you kept some kind of record on whether the amount you bought last year was enough. When we figure out how much seed to order we add in some extra for some things – crops that can be difficult to germinate, or we really don’t want to cut too close. We add 20 percent extra for most crops, but only 5 percent for kale, 10 percent for onions and collards and 30 percent for melons. These numbers are based on our experience – yours might be different. We also know which seed we can buy in bulk and use over several years. This gives us an additional security against poor germination, or plagues of grasshoppers or caterpillars. For me, a big bag of broccoli seed for each of our main varieties gives some kind of warm glow of horticultural security! Buying too much either leads to wasting money (if we throw it away) or wasting time and money (if we sow old seed that doesn’t come up well, then have a crop failure).

If you use spreadsheets, see my post Cooking Greens in December Special Topic: Ordering Seeds.

Here’s a helpful table of 1000 Seed Weight for 13 crops. Another of the challenges with seed ordering is converting between grams, ounces and seed counts – have your calculator at the ready, or easier still, just type “Convert ½ oz to grams”into your search engine.

 

  1. Choosing varieties.

See How to read seed catalogs for tips on getting what you really want by paying attention to what’s in the small print and what isn’t mentioned. We carefully look for varieties that offer the flavor, productivity and disease resistance we need. The catalogs are starting to appear in my mail box. The early bird catches the preferred varieties! The main companies we order from are Fedco Seeds, Johnny’s Selected Seeds and of course, Southern Exposure Seed Exchange. We like SESE for regionally adapted varieties, Fedco for great prices on bulk sizes, and Johnny’s for some varieties we really like that aren’t available from the other two.

 

  1. Formatting and placing seed orders

We grow lots of different crops, so we make a spreadsheet, and include columns for the name of the supplier we buy each variety from (we just use the initial), the item number in the catalog, the packet size and the price. (Be careful though, if you carry this information over from year to year – prices change.) Once we have composed our total seed order, we sort the orders by the name of the supplier. Then we can calculate the total price for each supplier. This also gives us the opportunity to look at price breaks for large orders and move an item from one supplier to another, if that makes sense. At this point we usually make a cup of tea and reward ourselves with an “impulse buy” or two, if that doesn’t push us up into a higher shipping cost bracket or blow the budget. We place our orders online these days, nice and early, to increase the chances of getting exactly what we want.

Here are a few more thoughts on crops to consider:

  1. Insurance crops that are there when you need them

Young Bright Lights chard.
Photo Pam Dawling

For an overall sense of success, grow some “Insurance Crops”. These are reliable vegetable crops that grow without much attention and quietly wait until needed. Chard is one of those. We sow chard in April, after the early spring rush. We plan for it to provide us with leafy greens in the summer, after the brassicas have bolted. We prepare a bed, unroll hay mulch over it, then make “nests” in the hay for planting. Nests are holes in the hay down to soil level, at each spot where we want to plant. After transplanting. we water and tuck the hay tight around the plants to keep the weeds at bay. Some years there isn’t much demand for chard and we just leave it growing. If we need it, there it is with a generous supply of leaves. If we ignore it, nothing goes wrong. It’s worth having some crops like this in the garden, to help ensure there’s always something to eat.

Malabar spinach.
Photo by Southern Exposure Seed Exchange

One year we grew Malabar spinach and it played a similar role: hot weather leafy cooking greens. Malabar can be used when small for salads, or when larger for cooking. It wasn’t hugely popular in either role, but it was beautiful. To be fair, I don’t think we did the best by it. Because it was new, and because it had the word “spinach” in its name, some cooks served large leaves for salad. Alone. I don’t recommend that.

Purple Pod asparagus bean,
Credit Southern Exposure Seed Exchange

Another insurance crop for us is asparagus beans, also known as yard long beans. Once trellised, the plants need no attention, other than regular picking. If not picked, the pods grow puffy and useless, so this is not a crop to ignore for too long. Asparagus beans are related to southern peas (cowpeas), and are more resistant to Mexican bean beetles than regular green beans are. They do need trellising, but once you’ve done that, the same plants will feed you all season. Very little seems to trouble them.

West Indian gherkins on a trellis.
Photo by Nina Gentle

While we’re on the topic of crops that do need trellising, but can then produce all season, I’ll add in the West Indian gherkins. I found I did need to tuck these plants into the netting, so they weren’t work free. But the plants were disease-free and very productive. If you have trouble with regular pickling cucumbers, you might sow some of these as well, to be sure of being able to have something to pickle.

Another insurance crop is Tokyo bekana, or its cousin Maruba Santoh in late summer as a substitute for lettuce. It can be hard to germinate lettuce in hot weather, but these tender brassicas germinate under hot conditions and produce fast-growing very tender leaves with crunchy stems. Some people don’t know they’re not eating lettuce!

Tokyo bekana and spinach in October.
Photo Wren Vile

Senposai is a cooking green that does well in spring and fall outdoors, and in our hoophouse in the winter. It’s fast-growing, productive, disease-resistant, easy to cook and delicious to eat.  In spring it needs an early start in our climate, so that it has time to be productive before it bolts. In fall it’s cold-hardy down to 12F.  Its Achilles Heel is that it can really attract Harlequin bugs! We did spend time every day for a while squashing the bugs on the senposai leaves, and we made a difference in the number of bugs.

Well, I hope this has given you some thoughts about ordering seeds of some insurance crops for next year, when you plan your seed order.

  1. VEGETABLE CROPS THAT OFFER FAST RETURNS

Because things can go wrong in agriculture, (we are, after all, not in control of the universe!) I like to have on hand seeds for fast-growing crops that can fill unexpected gaps.

Some Eat-All Greens in early November.
Photo Lori Katz
  1. Eat-All Greens

Carol Deppe, in her delightful book The Tao of Vegetable Gardening introduces us to the concept of Eat-All Greens. Carol grows these by broadcasting seed of one of her carefully chosen greens crops in a small patch. When it reaches 12″ tall, she cuts the top 9″ off for cooking, leaving the tough-stemmed lower part, perhaps for a second cut, or to return to the soil. I wanted to try this idea in Virginia, where the climate is fairly different from the Pacific Northwest where Carol lives. I decided fall was a promising time of year to try this scheme, as our spring planted greens only have a short season before they bolt. And summer is too hot, winter too cold. . . We sowed in mid-September.

These can also be insurance crops, in that, if you don’t need them, you can cut and compost them, to let fresh leaves grow. I wrote three posts on Eat-All Greens, because they were such fun and so productive

Winter Preparations for Vegetable Gardens

 

Frosty daikon radish
Photo by Bridget Aleshire

Winter-Kill Temperatures

My annual blogpost of Winter-Kill Temperatures for Cold-Hardy Vegetables is always very popular. In fact, it’s my most popular title! Usually searches for this info increase in October and peak in early November, so here are quick links for those of you who have been meaning to look something up.

Winter-Kill Temperatures of Cold-Hardy Vegetables 2020

Winter Kill Temperatures of Cold-Hardy Vegetables 2019

Winter-Kill Temperatures of Cold-Hardy Vegetables 2018

Winter Kill Temperatures of Winter-Hardy Vegetables 2016

Trimming roots from a leek in December.
Photo Pam Dawling

For several years, starting in 2012, my friend and neighboring grower Ken Bezilla of Southern Exposure Seed Exchange and I have been keeping records of how well our crops do in the colder season. Ken provided much of the original information, and has suggested the morbidly named Death Bed idea: set aside a small bed and plant a few of each plant in it to audition for winter hardiness. Note each increasingly cold minimum temperature and when the various crops die of cold, to fine-tune your planting for next year (and leave me a comment!) Each year I update the list, based on new things I learned during the recent winter.

We are in zone 7a, with an average annual minimum temperature of 0-5°F (-18°C to -15°C).

The winter 2019-2020 was mild, with our lowest temperature being a single night at 12°F (-11°C). The Koji greens became completely unmarketable but did not completely die. Yukina Savoy is indeed hardier (as I expected), being OK down to 10°F (-12°C). We had one night at 13°F (-10°C) and two each at 17°F (-8°C), 18°F (-8°C also) and 19°F (-7°C). That winter I noted the death of rhubarb stems and leaves at 25°F (-4°C), rather than 22°F (-6°C), as I noted a year or two ago. I also added some cover crop hardiness temperatures.

Rhubarb in spring.
Photo Kathryn Simmons

I also learned that there is more damage when the weather switches suddenly from warm to cold. And that the weatherman in Raleigh, NC says it needs 3 hours at the critical temperature to do damage. Also note that repeated cold temperatures can kill off crops that can survive a single dip to a low temperature, and that cold winds, or cold wet weather can destroy plants quicker than simple cold. All greens do a lot better with row cover to protect them against cold drying winds.

Winter hoophouse lettuce
Photo Kathryn Simmons

It’s worth noting that in a double-layer hoophouse (8F/5C warmer at night than outside) plants can survive 14F/8C colder than they can outside, without extra rowcover; at least 21F/12C colder than outside with thick rowcover

Salad greens in a hoophouse in zone 7 can survive nights with outdoor lows of 14°F (-10°C). A test year: Lettuce, Mizuna, Turnips, Russian kales, Senposai, Tyee spinach, Tatsoi, Yukina Savoy survived a hoophouse temperature of 10.4°F (-12°C) without rowcover, -2.2°F (-19°C) with. Bright Lights chard got frozen leaf stems.

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Seeking Reader Participation

Your experience with your soils, microclimates and rain levels may lead you to use different temperatures. I’d love to hear from readers if they’ve found my numbers work for them, or if they have a different experience. You can leave a comment here, and it will appear on the website, for others to consider. Or you can fill out a Comment Page and only I will see it, although I’ll pass on the information without your name, if I think others would like to know too.

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Preparing for winter

Rowcover rolling with crank handle.
Photo Rodaew Institute

I’ve also written posts about winter preparations

Getting ready for frost. This post includes info on DIY weather-forecasting, our Frost Prediction checklist, and our Frost Alert Card. Also a link to a 126 page book which includes explanations of freezes and frosts to help us make sense of advice we’ve not understood. FrostProtectionFundamentalsPracticeandEconomicsFAO.pdf

Preparing for Frost and Cold Weather. This post includes our Frost Alert Card, a Frost Predictions checklist of what to do when the first fall frost is expected; how to use sprinklers overnight to stop tomatoes from freezing; four ranges of cold-hardiness (some crops can wait in the garden till it gets colder); and different levels of crop protection, including rowcover, low tunnels, Quick Hoops, caterpillar tunnels and hoophouses (aka high tunnels).

Season Extension and Frost Preparations. This post includes my Season Extension slideshow; the Frost Alert Card and Frost Predictions checklist again; a diagram of our winter double hoop system to hold rowcover in place during the worst weather;

Double hoop system for winter rowcover.
Pam Dawling

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Changing Winter Temperatures

Here’s an article from the Virginia Mercury by Sarah Vogelsong, giving info about changing winter temperatures, particularly later fall frosts in Virginia:

The frozen Potomac River. (Sarah Vogelsong/Virginia Mercury)

Autumn’s first frost is falling later. For farmers, the consequences are wide-ranging

by Sarah Vogelsong, November 3, 2020

Halloween has come and gone. The clocks have been set back. Every evening darkness falls just a little bit earlier.

But for much of Virginia, the first frost still remains elusive.

Over the past century, the average date of the first frost has been moving progressively backward throughout the commonwealth, today landing a week or more later than it did at the turn of the 20th century.

“This is one of the clearest signs of not only the changing climate but … its impact on our systems,” said Jeremy Hoffman, who as chief scientist at the Science Museum of Virginia conducts extensive research on climate change in Virginia. “It’s not just here, it’s everywhere.”

As global temperatures have warmed, largely due to the release of greenhouse gases into the atmosphere, frost seasons have shrunk. The Fourth National Climate Assessment released by the Trump administration in 2018 reported that “the length of the frost-free season, from the last freeze in spring to the first freeze of autumn, has increased for all regions since the early 1900s.”

How the shifts have played out in different states with different geographic, ecological and topographic features varies. Data from the U.S. Environmental Protection Agency show that between 1895 and 2016, the average date of the first fall frost moved back by 7.1 days in Virginia.

On the local level, the changes may be even starker. Estimates of how much the average date has changed vary depending on the time range used and how scientists fit a line to their data points, but in most Virginia cities, they show unmistakable upward trends. Looking at first frost dates between 1970 and 2016, Climate Central, a nonprofit staffed by scientists and journalists, calculated that on average, the first frost today is 5.9 days later in Lynchburg, 8.9 days later in Harrisonburg, 12.8 days later in Roanoke, 15 days later in Charlottesville and 18.5 days later in Richmond. While their data show Norfolk’s first frost occurring about six days earlier on average, Hoffman said that longer-range data going back to 1940 show the first frost moving back by about five days. Still, he cautioned, variation does occur: “Localized things like weather” can “work against that dominant signal in datasets like these.”

First freeze dates for Richmond, 1930-2019. (Jeremy Hoffman, Science Museum of Virginia)

The implications of the shifts in the freezing season go beyond a few more days to enjoy warm weather, say scientists and policymakers. Perhaps most affected are farmers, whose livelihood is intimately tied to fluctuations in both short-term weather and long-term climate.

“Some things you can sort of manage around and some things you can’t,” said Wade Thomason, a professor of crop and soil environmental science at Virginia Tech and the state’s grain crops extension specialist.

For most farmers, the last frost of the year in the spring is the riskier of the season’s two endpoints, falling as it does when most plants are young and more vulnerable to temperature extremes. But ongoing changes in the first frost in the fall also have ripple effects.

“It can be a beneficial thing for some instances. We might get more grazing days for livestock operations in a year,” said Thomason. For some crops, like double-cropped soybeans that are planted following the harvest of another crop — typically a grain like wheat — “it can extend the season.”

Other effects are less immediately apparent. Many wheat farmers who typically plant in mid-October have begun to push back their planting dates to ensure plants don’t grow too quickly during the freezing months, making them susceptible to disease or falling over in the field. Specific types of forage rely on long periods of cool weather to thrive: in Northern Virginia and the Shenandoah Valley, farmers have noticed that orchard-grass stands are only living for four to five years instead of the once-standard 10.

“For years now, we’ve heard from farmers that the stands don’t persist like they used to,” said Thomason. Research has shown that one factor contributing to less persistence is warmer nighttime temperatures, he added, but because most operations rely on cultivars developed decades ago, “we haven’t adapted orchard grass that thrives in a warmer climate.”

Other crops affected by longer warm seasons? Tree fruits and wine grapes

“Virginia’s one of those places that we expect to get hotter and we also expect to get wetter,” said Benjamin Cook, a climate scientist with the National Aeronautics and Space Administration’s Goddard Institute for Space Studies whose research includes the effects of climate change on vineyards. Neither of those conditions are necessarily good for high-quality wine prospects, he said. Furthermore, farmers working in these areas face special risks because of the long time to maturity of their crops.

“Those are parts of the agricultural world that adaptation eventually becomes a lot more challenging, because you can’t switch crops from year to year,” he said. “You have to make a bet on something and wait four years to see if it pays off.”

Regardless of their specialty, all farmers face another consequence of shorter freeze seasons: more weeds and more pests.

“With longer growing seasons, with these warmer winters, the populations of insects are increasing, the mortality is lower, they can produce more generations a year, and that potentially presents a problem for agriculture and plants in general,” said Cook.

Those effects can be seen on the ground, said Thomason: “Maybe 30 years ago, we could stop worrying about them in early October, and now it may be a week or 10 days later.”

https://www.virginiamercury.com/ Virginia Mercury is part of States Newsroom, a network of news outlets supported by grants and a coalition of donors as a 501c(3) public charity. Virginia Mercury maintains editorial independence. Contact Editor Robert Zullo for questions: [email protected] Follow Virginia Mercury on https://facebook.com/thevirginiamercury and https://twitter.com/MercuryVirginia

Our stories may be republished online or in print under Creative Commons license CC BY-NC-ND 4.0. We ask that you edit only for style or to shorten, provide proper attribution and link to our web site.

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Growing and Saving Seeds: my Seed Garden Slideshow and a Cuban Bean Seed Bank

 

At the Organic Growers School Spring Conference I gave my presentation The Seed Garden, about combining growing some seed crops alongside lots of vegetable crops – a way for vegetable growers to diversify and grow seed of a few special crops either for themselves or to sell for some extra income and to keep a chosen variety available. I included information on selecting desirable characteristics and making an improved strain of that variety.

You can watch the slideshow here, by clicking on the diagonal arrow to increase the screen size and then the right pointing triangular arrow:

I also took the opportunity to add a few more of my slideshows to my collection on SlideShare.

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Meanwhile I’ve been sorting out more photos from my Cuba trip, and I want to tell you about a bean seed bank at Finca Hoyo Bonito I visited during our day traveling from Havana, west for three hours to the Viñales Valley in the province of Pinar del Rio.

The seed farm has a bank containing 250 varieties of bean seed. It’s a hobby for the retired woman growing and saving the beans. Her goal is to get a hundred pounds of each variety. She gives bean seed to any farmer who asks, with no requirement to return the investment. (this is different from some seed banks, which require growers to repay the “loan”)

Finca Hoyo Bonito bean seed bank, Pinar del Rio, Cuba
250 bean seed varieties are kept in this tiny seed bank.
The Seed Conservator, or Banker at Finca Hoyo Bonito. Note the reuse of ubiquitous plastic water bottles to store some of the seeds. Tourists need to drink only bottled water.
Bean seed has a limited shelf life, and so must be grown out frequently.
Here is a display of just some of the bean varieties.
Finca Hoyo Bonito Bean Seed Bank, Pinar del Rio, Cuba

Here is a short video about Finca Hoyo Bonito. It’s in Spanish, naturally!

Winter-Kill Temperatures of Cold-Hardy Vegetables 2020

Overwintered Vates kale in central Virginia in March.
Photo Nina Gentle

At the Organic Association of Kentucky Conference, I gave a a presentation on Winter High Tunnel and Outdoor Vegetable Production. You can see it here. Click on the diagonal arrow icon to see it full screen, then click on the right pointing triangular arrow

Winter-Kill Temperatures of Cold-Hardy Vegetables 2020

I keep records of how well our crops do in the colder season, both outdoors and in our double-layer hoophouse. I note each increasingly cold minimum temperature and when the various crops die of cold, to fine-tune our planning for next year. We are in zone 7a, with an average annual minimum temperature of 0-5°F (-18°C to -15°C). 

The winter 2019-2020 has been mild, with our lowest temperature being a single night at 12°F (-11°C). The Koji became completely unmarketable but did not completely die. Yukina Savoy is indeed hardier, being OK down to 10°F (-12°C). We had one night at 13°F (-10°C) and two each at 17°F (-8°C), 18°F (-8°C also) and 19°F (-7°C).

This winter I noted the death of rhubarb stems and leaves at 25°F (-4°C), rather than 22°F (-6°C), as I noted a year or two ago.

In early January 2018, we had some extremely cold temperatures of -8°F and -9°F (-22°C and -23°C). The winter of 2018-2019 was not as brutal. Our lowest temperatures were 6°F (-14°C) in late January, 8°F (-13°C) in December 2018 and a couple of 11°F (-12°C). I found that senposai is more cold-tolerant than I had thought. Averaging our winter low over those three winters gives 3.2°F (-16°C), completely within the zone 7a range.

My other results from other years still hold up.

I also learned that there is more damage when the weather switches suddenly from warm to cold. And that the weatherman in Raleigh, NC says it needs 3 hours at the critical temperature to do damage.

Radicchio seeds from Seeds from Italy

Notes on Chicories and Endives

We gave up growing chicories and endives because we really didn’t like the bitterness. I decided to do some more online research to make sure I wasn’t spreading untruths. Chicories and endives fall into two groups, but they are confusing because the common names sometimes suggest the opposite group than they are botanically. Here’s the best info I have. If you know differently, please leave a comment.

Cichorium intybus, commonly called chicories, are mostly heading crops. The group includes radicchio, both Treviso and Chioggia (hardy to about 20°F (-7°C). Belgian Witloof endive (the kind for forcing chicons) is also a chicory. It dies at 25°F (-4°C). Sugarloaf chicory is the least hardy chicory, and dies at 27°F (-3°C).

Cichorium endivia, commonly called endives, are mostly loose-leaf crops, less cold-hardy than intybus types (chicories). This group includes Frisée types and escaroles, which are also known as Batavian endives. They generally survive down to 22°F (-6°C), although Perfect and President endives can survive down to 10°F (-12°C) – can anyone confirm or deny this?

Using the List

Unless otherwise stated, these are killing temperatures of crops outdoors without any rowcover. All greens do a lot better with protection against cold drying winds. Note that repeated cold temperatures can kill crops that can survive a single dip to a low temperature, and that cold winds, or cold wet weather can destroy plants quicker than simple cold. Your own experience with your soils, microclimates and rain levels may lead you to use different temperatures in your crop planning.

Hoophouse beds in November.
Photo Ethan Hirsh

Hoophouse Notes

Our double-plastic hoophouse keeps night time temperatures about 8F (4.5C) degrees warmer than outdoors, sometimes 10F (5.5C) degrees warmer. Plus, plants tolerate lower temperatures inside a hoophouse. The soil stays warmer; the plants recover in the warmer daytime conditions (it seems to be the night+day average temperature that counts);

In the hoophouse (8F (4.5C) degrees warmer than outside) plants without extra rowcover can survive 14F (7.7C) degrees colder than they could survive outside; with thick rowcover (1.25oz Typar/Xavan) at least 21F (11.6C) degrees colder than outside.

For example, salad greens in our hoophouse can survive nights with outdoor lows of 14°F (-10°C). Russian kales, lettuce, mizuna, senposai, spinach, tatsoi, turnips, Yukina Savoy survived a hoophouse temperature of 10.4°F (-12°C) without rowcover, -2.2°F (-19°C) with. Bright Lights chard got frozen leaf stems.

Young Bright Lights chard.
Photo Pam Dawling

Lettuce varieties for a solar-heated winter greenhouse or hoophouse in zone 7a: (hardiest are in bold) Buckley, Ezrilla, Green Forest, Green Star, Hampton, Hyper Red Rumpled Wave, Marvel of Four Seasons, Merlot, New Red Fire, North Pole bibb, Oscarde, Outredgeous, Pirat, Red Cross bibb, Red Sails, Red Salad Bowl, Red Tinged Winter, Revolution, Rouge d’Hiver, Salad Bowl, Sylvesta bibb, Tango, Winter Marvel, Winter Wonderland.

Outdoor killing temperatures of crops (unprotected unless stated)

35°F (2°C):  Basil.

32°F (0°C):  Bush beans, some cauliflower curds, corn, cowpeas, cucumbers, eggplant, limas, melons, okra, some pak choy, peanuts, peppers, potato vines, squash vines, sweet potato vines, tomatoes.

27°F (-3°C): Many cabbage varieties, Sugarloaf chicory (takes only light frosts).

25°F (-4°C): Some cabbage, chervil, Belgian Witloof chicory roots for chicons, and hearts, Chinese Napa cabbage (Blues), dill (Fernleaf), some fava beans (Windsor), annual fennel, some mustards (Red Giant, Southern Curled) and Asian greens (Maruba Santoh, mizuna, most pak choy, Tokyo Bekana), onion scallions (some are much more hardy), radicchio, rhubarb stems and leaves.

Tokyo bekana in our hoophouse.
Photo Twin Oaks Community

22°F (-6°C): Some arugula (some varieties are hardier), Bright Lights chard, endive (Escarole may be a little more frost-hardy than Frisée), large leaves of lettuce (protected hearts and small plants will survive colder temperatures).

20°F (-7°C): Some beets (Bulls Blood, Chioggia,), broccoli heads (maybe OK to 15°F (-9.5°C)), Brussels sprouts, some cabbages (the insides may still be good even if the outer leaves are damaged), some cauliflower varieties, celeriac, celtuce (stem lettuce), some head lettuce, some mustards/Asian greens (Tendergreen, Tyfon Holland greens), flat leaf parsley, radicchio, both Treviso and Chioggia, radishes (Cherry Belle), most turnips (Noir d’Hiver is the most cold-tolerant variety).

Large oat plants will get serious cold damage. Oats seedlings die at 17°F (-8°C)

Canadian (spring) field peas are hardy to 10-20°F (-12 to -7°C).

15°F (-9.5°C): Some beets (Albina Verduna, Lutz Winterkeeper), beet leaves, some broccoli, some cabbage (Kaitlin, Tribute), covered celery (Ventura), red chard, cilantro, fava beans (Aquadulce Claudia), Red Russian and White Russian kales, kohlrabi, some lettuce, especially medium-sized plants with 4-10 leaves (Marvel of Four Seasons, Olga, Rouge d’hiver, Tango, Winter Density), curly leaf parsley, rutabagas (American Purple Top Yellow, Laurentian), broad leaf sorrel, most covered turnips, winter cress.

Young Cylindra beets.
Photo Wren VIle

12°F (-11°C): Some beets (Cylindra,), some broccoli perhaps, Brussels sprouts, some cabbage (January King, Savoy types), carrots (Danvers, Oxheart), most collards, some fava beans (mostly cover crop varieties), garlic tops if fairly large, Koji greens, most fall or summer varieties of leeks (Lincoln, King Richard), large tops of potato onions, covered rutabagas, some turnips (Purple Top).

10°F (-12°C): Covered beets, Purple Sprouting broccoli for spring harvest, a few cabbages (Deadon), chard (green chard is hardier than multi-colored types), some collards (Morris Heading can survive at least one night at 10F), Belle Isle upland cress, some endive (Perfect, President), young Bronze fennel, Blue Ridge kale, probably Komatsuna, some leeks (American Flag, Jaune du Poiteau), some covered lettuce (Pirat, Red Salad Bowl, Salad Bowl, Sylvesta, Winter Marvel), covered winter radish (Daikon, China Rose, Shunkyo Semi-Long survive 10°F/-12°C), Senposai leaves (the core of the plant may survive 8°F/-13°C), large leaves of savoyed spinach (more hardy than smooth-leafed varieties), Tatsoi, Yukina Savoy.

Oats cover crop of a medium size die around 10°F (-12°C). Large oat plants will die completely at 6°F (-17°C) or even milder than that.

5°F (-15°C): Garlic tops even if small, some kale (Winterbor, Westland Winter), some leeks (Bulgarian Giant, Laura), some bulb onions, potato onions and other multiplier onions, smaller leaves of savoy spinach and broad leaf sorrel. Many of the Even’ Star Ice Bred greens varieties are hardy down to 6°F (-14°C), a few unprotected lettuces if small (Winter Marvel, Tango, North Pole, Green Forest).

Garlic shoots in January.
Photo Pam Dawling

0°F (-18°C): Chives, some collards (Blue Max, Winner), corn salad (mâche), garlic, horseradish, Jerusalem artichokes, Even’ Star Ice-Bred Smooth Leaf kale, a few leeks (Alaska, Durabel, Tadorna); some bulb onions, yellow potato onions, some onion scallions, (Evergreen Winter Hardy White, White Lisbon), parsnips (probably even colder), salad burnet, salsify (?), some spinach (Bloomsdale Savoy, Olympia). Walla Walla onions sown in late summer are said to be hardy down to -10°F (-23°C), but I don’t trust below 0°F (-18°C)

Crimson clover is hardy down to 0°F (-18°C) or slightly colder

 -5°F (-19°C): Leaves of overwintering varieties of cauliflower, Vates kale survives although some leaves may be too damaged to use.

-10°F (-23°C) Austrian Winter Field Peas and Crimson clover (used as cover crops).

-15°F (-26°C) Hairy vetch cover crop – some say down to -30°F (-34°C)

-20°F (-29°C) Dutch White clover cover crops – or even -30°F (-34°C)

 -30°F to -40°F (-34°C to -40°C): Narrow leaf sorrel, Claytonia and some cabbage are said to be hardy in zone 3. I have no personal experience of this.

 -40°F (-40°C) Winter wheat and winter rye (cover crops).