Winter-Kill Temperatures of Cold-Hardy Vegetables 2021

Our pond iced over.
Photo Ezra Freeman

Winter-Kill Temperatures of Cold-Hardy Vegetables 2021

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 2020-2021 was mild, with our lowest temperature being a single late January night at 10°F (-12°C). We had one night at 11°F (-12°C) one at 17°F (-8°C), three at 18°F (-8°C also) and one at 19°F (-7°C). very little snow or ice. Similar to temperatures in the 2019-2020 winter.

The winter of 2018-2019 had lowest temperatures of 6°F (-14°C) in late January 2019, 8°F (-13°C) in December 2018 and a couple of 11°F (-12°C). In early January 2018, we had some extremely cold temperatures of -8°F and -9°F (-22°C and -23°C). Averaging our winter low over those four winters 2017-2021 gives 4.8°F (-15°C), within the zone 7a range.

Georgia Cabbage Collards, good down to 20F (-7C) Photo Southern Exposure Seed Exchange

New Info this winter

I’ve added in some temperatures for collard varieties (Georgia Cabbage collards, McCormack’s Green Glaze, variegated collards) from the Heirloom Collards Project, and also gained some info on spinach (Long Standing Bloomsdale), kales (Rainbow Mix Lacinato) and mustards (Chinese Thick-Stem) from Southern Exposure Seed Exchange. I’ve added in their suggestions on cold-tolerant early spring lettuces, Crawford, Simpson Elite, Susan’s Red Bibb and Swordleaf.

My results from other years still hold up.

Swordleaf lettuce on the right with another lettuce and radishes in spring.
Photo Bridget Aleshire

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. Crops get more damage when the weather switches suddenly from warm to cold. If the temperature drops 5 or more Fahrenheit degrees (about 3 C degrees) from recent temperatures, there can be cold damage. The weatherman in Raleigh, NC says it needs 3 hours at the critical temperature to do damage. Your own experience with your soils, microclimates and rain levels may lead you to use different temperatures in your crop planning.

Reflect spinach in the open got damaged but not killed at -9F.
Photo Pam Dawling

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.

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)), some 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 collards (Georgia Cabbage Collards, variegated collards), 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).

Ruby chard, good down to 15°F (-9.5°C). hardier than Bright Lights, but less hardy than green chard varieties.
Photo Kathryn Simmons

15°F (-9.5°C): Some beets (Albina Verduna, Lutz Winterkeeper), beet leaves, some broccoli and cauliflower leaves, 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.

12°F (-11°C): Some beets (Cylindra,), some broccoli perhaps, some 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 10°F), Belle Isle upland cress, some endive (Perfect, President), young Bronze fennel, Blue Ridge kale, probably Komatsuna, some leeks (American Flag (Broad London), Jaune du Poiteau), some covered lettuce (Pirat, Red Salad Bowl, Salad Bowl, Sylvesta, Winter Marvel), Chinese Thick-Stem Mustard may survive down to 6°F (-14°C), 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.

Garlic shoots poking through the mulch in January. Survive down to 5°F (-15°C), and if killed, will regrow from underground.
Photo Pam Dawling

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 and the Ice-Bred White Egg turnip are hardy down to 6°F (-14°C), a few unprotected lettuces if small (Winter Marvel, Tango, North Pole, Green Forest).

0°F (-18°C): Chives, some collards (Blue Max, Winner, McCormack’s Green Glaze), 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, Long Standing Bloomsdale,  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 perhaps as cold as -10°F (-23°C)

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

A cover crop mix of winter rye, hairy vetch and crimson clover.
Credit Kathryn Simmons

-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).

Hoophouse Notes

Winter crops snug in our hoophouse in a December snowstorm.
Photo Pam Dawling

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.

Lettuce Notes

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, Oscarde, Outredgeous, Pirat, Red Cross, Red Sails, Red Salad Bowl, Red Tinged Winter, Revolution, Rouge d’Hiver, Salad Bowl, Sylvesta, Tango, Winter Marvel, Winter Wonderland.

Cold-tolerant early spring lettuces include Buckley, Crawford, Green Forest, Hampton, Merlot, New Red Fire, Revolution, Simpson Elite, Susan’s Red Bibb and Swordleaf.

Notes on Chicories and Endives

Verona Red radicchio, hardy to about 20°F (-7°C).
Photo Southern Exposure Seed Exchange

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.

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?

© Pam Dawling 2021


Go to my Events Page for more information on these online events

Mother Earth News Fair Online: Food Independence Course Part Two was released on 3/26/21.

It consists of eight video presentations, most of which come with pdf handouts. My contribution is Growing Asian Greens, and pairs nicely with Guide to Asian Vegetables with Wendy Kiang-Spray, author of The Chinese Kitchen Garden: Growing Techniques and Family Recipes from a Classic Cuisine. Other topics include Dandelion Wine, Homemade Teas, Food Conversations, Passive Solar Greenhouse Design, Productive Growing from Home, and Growing Your Own Spices.

You can subscribe to the All-Access Bundle for $2.99/month (or $35 for a year).

My previous contribution is an 8-part Garden Planning Course

I also did a workshop on Winter Cover Crops for Gardeners as part of the Winter Gardening Course.

All these and many more videos and handouts are available as part of the All-Access Bundle.

 

Early Lettuce Production

Young Salad Bowl lettuce
Photo Wren Vile

Early Lettuce Production

Growing early season lettuces involves choosing suitable types and varieties (cold-tolerant and fast-growing), having successful production methods, and a good schedule. Harvesting early in the year might mean fast production in January and February, or it might mean starting in the fall and overwintering the plants. See my post series Lettuce of the Month, for ideas on varieties and techniques throughout the year.

Our Climate Zone in central Virginia is 7a, which means our annual minimum temperature averages 0°F to 5°F (-18 to -15°C).  The average date of the last spring frost is April 30 (later than 5/14 one year in 10). We grow lettuce outside from transplants from February to December, in a solar greenhouse from October to early March, and in a solar-heated double-layer hoophouse from October to April.

Swordleaf, Red Salad Bowl and Bronze Arrow lettuces.
Photo Bridget Aleshire

Lettuce Types

There are several different general types of lettuces. In terms of growing speed, the baby lettuce mixes and the leaf lettuces produce harvests soonest after sowing. Loose-leaf lettuces are very useful because you can harvest individual leaves while you’re waiting for the heads to reach full size.

Leaf types are ready for harvest 45-60 days from direct seeding, 30-45 days from transplanting. Bibbs mature in 60-75 days, most head lettuce need up to 80 days from seeding, or 60-70 days from transplanting in spring. Romaines are slower-growing (70 days or more). Batavian lettuces (also called French Crisp) are tasty, thick-leafed varieties that have excellent heat and cold tolerance. Icebergs mature in 75-100 days.

Beautiful baby lettuce mix in our hoophouse.
photo Wren Vile

Baby lettuce can be cut 21 days from seeding, (except from November to mid-February, when it may take 2 or 3 times as long).

Bolt-resistance generally goes from Leaf types (first to bolt), through Romaines, Butterheads, Bibbs, to Crispheads.

I like to sow four lettuce varieties each time (for the attractive harvests, and to reduce the risks if one variety bolts or suffers disease): at least one red and one romaine. We have 5 lettuce seasons, with different varieties:

  1. Early Spring (Jan – Mar), 6 sowings
  2. Spring (April – May 15), 5 sowings
  3. Summer (May 15 – Aug 15), 17 sowings
  4. Fall (Aug 15 – Sept 7), 9 sowings
  5. Winter indoors, Sept 8 – 27, 9 sowings

 Lettuce Varieties

Bronze Arrow lettuce ultra-closeup. Photo Bridget Aleshire

It’s important to grow the right lettuce variety for the conditions. For earliest harvests, consider a different, faster, variety than you have usually grown. Some of the early spring lettuce varieties are often useless here if sown after mid-March, or even mid-February, because they bolt prematurely as the Virginia spring flips from cold to hot (and back again, grrr!). Varieties we only sow until 2/15 include Bronze Arrowhead (46 day leaf lettuce); Buckley, Ezrilla and Hampton (55d multi-leaf types); Merlot (60d), Midnight Ruffles (48d) and Oscarde (45d) (leaf lettuces). Antares (48d) Panisse (48d) and Revolution (38d) leaf lettuces we can sow until 3/15.

Nancy bibb lettuce
Photo Bridget Aleshire

Others that we like in early spring go on to be useful later in spring too. In this category are Buttercrunch (a small 50d bibb); Nancy (58d) and Sylvesta (52d) (two big green bibbs); Pirat (55d red bibb), Green Forest (56d), Kalura (57d) (two green romaines); and New Red Fire (55d), our reliable Salad Bowl (45d) and Red Salad Bowl (46d), Starfighter (52d), and Swordleaf (53d) (leaf lettuces)

New Red Fire lettuce.
Photo by Bridget Aleshire

The baby lettuce mixes we like are Fedco’s 2981 LO Lettuce Mix OG (contains at least six different lettuces) or Johnny’s Allstar Gourmet Lettuce Mix #2310 (including green and red oakleaf, green and red romaine, lollo rossa, and red leaf lettuces). One gram sows 25 ft, one ounce will sow about 600 feet.

For those with challenging growing conditions, both companies offer other specialized selected mixes.

Cold-tolerance of lettuce

Red Tinged Winter and Tango lettuce in our hoophouse in December.
Photo Pam Dawling

Lettuce is more cold tolerant than many people realize. If plants are sufficiently hardened (prepared by growing in gradually lower temperatures), they can withstand freezing. At 22°F (-6°C), large leaves of some lettuce will die. Medium-sized plants with 4-10 leaves (Marvel of Four Seasons, Olga, Rouge d’Hiver, Tango, Winter Density may survive unprotected down to 15°F (-9.5°C). Half-grown lettuces are more cold-hardy than full-sized plants.

Lettuce Crop Requirements

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

Lettuce seed remains dormant unless triggered by adequate levels of light and temperature. It needs light to germinate, so don’t sow too deep: ¼-3/8″ (6-9 mm) is enough. Some sources recommend not covering the seed at all, but this can make it hard to keep the seed damp. The light dormancy is more pronounced in fresh seed, which has higher levels of the hormone that controls germination.

Soil temperature is important. I have a table of optimum soil temperatures for germination in The Year-Round Hoophouse The optimum temperature range for lettuce germination is 68-80°F (20-27°C). It takes 7 days to germinate with a soil temperature of 50°F (10°C) or 15 days at 41°F (5°C), and only 4 days at 59°F (15°C). Even a few hours at temperatures higher than the optimum can induce dormancy.

Lettuce transplants prefer a well-draining soil high in organic matter, and with a pH of 6.0-7.0, not lower. Optimum growing temperatures are 60-65°F (15-18°C), with a minimum of 40°F (4.5°C) for any growth to occur. Lack of water will lead to bolting, and/or bitterness. Keep them growing quickly for good flavor.

Lettuce in January

A flat of newly emerged lettuce seedlings
Photo Kathryn Simmons

We plan to start harvesting heads of lettuce outdoors from April 15. Before then we will harvesting lettuce in our greenhouse and hoophouse.

In mid-January we sow four lettuce varieties, to become our first outdoor transplants. I recommend sowing several varieties each time to spread your risks, if one kind bolts or suffers disease. I choose varieties that cover the range of colors and shapes. I select hardy types that are fast-maturing. Buttercrunch green bibb lettuce is one of my favorites for early spring. One of the Salad Bowl lettuces, red or green, is also usually in my first sowing. The Salad Bowls are so reliable and productive! New Red Fire has become another reliable lettuce stand-by for us. It was suggested to me by neighboring Virginia farmer, Gary Scott of Twin Springs Farm. It is more of a leaf lettuce, and doesn’t exactly head up, although it can be cut as admittedly lightweight heads. It works fine as a leaf lettuce, harvested by the cut-and-come-again method. We grow New Red Fire year round, it’s that adaptable and easy-going. We haven’t found many good full-size red romaines. Bronze Arrow  has worked well for us and we were harvesting it in early May.

We grow all our outdoor lettuce as transplants. In spring we sow in 3″ (7.5cm) deep open wood seed flats, 12″ x 24″ (30 x 60cm). We make four little furrows by pressing a 12″ (30 cm) plastic strip (aka a ruler!) into the seed compost. We sow the seed, label it, cover it lightly, water, and put the seeded flats in our germinator cabinet. The first flat of the year takes about 9 days to germinate.

Spotting cabbage seedlings from a seed flat into a transplant flat.
Photo Wren Vile

Once the seedlings are big enough to handle, we spot them out into 4″ (10 cm) deep flats (also 12″ x 24″/30 x 60cm). We have a plywood dibble board with pegs evenly spaced about 2.5″ (6 cm) apart. We aim to harden off the lettuce for two weeks in the cold frame before transplanting into the garden beds with thick rowcover on hoops to protect the lettuce from the still-cold outdoors. To be ready for harvest 4/15, these seeds have to become full size lettuces in 88 chilly days.

Seeds can instead be sown in cell packs or plug flats, putting three seeds in each cell, and later reducing to one seedling with scissors. Cells or pots with diameters from 1-2½” (2.5-6cm) can be used. The 96-cell size (1×1½”/2.5x4cm) works well, although the 200-cell size (1×1”/2.5×2.5cm) is possible if you can be sure to get the transplants out before they get root-bound. If warm germination space is limited in early spring, sow seed in a small flat, then “spot” the tiny seedlings into bigger flats, 606 (2×2¼”/2.5x6cm) cell packs, or 32-pack square pots to grow on in cooler conditions before planting out. Soil blocks are also possible, but take more time.

We make a second sowing on January 31. The intervals between sowings at the beginning of the year are long, because later sowings will catch up to some extent with earlier ones. Most crops grow faster in warmer weather.

Lettuce in February

We sow lettuce twice in February – 14 days apart. We get ready to transplant our first outdoor lettuce, to feed us mid-late April. Our first sowing of baby lettuce mix in the hoophouse comes to the bitter end, and the second sowing is awaited. We continue to harvest leaves from the large lettuce we transplanted in the hoophouse in October.

Lettuce in March

Lettuce with sclerotinia drop.
Photo Pam Dawling

We sow flats of lettuce every 10 days in March. March 9 is our goal for a transplanting date outdoors for our first 120 lettuce (about one week’s worth for 100 people).

Here is a link to a helpful publication from eXtension: Disease Management in Organic Lettuce Production. Horribly useful photos!

Baby Lettuce Mix

Baby lettuce mix can be ready in as little as 21 days from mid-spring to mid-fall, longer in early spring. A direct-sown cut-and-come-again crop, the plants regrow and can be harvested more than once in cool seasons. We sow 10 rows in a 4’ (1.2m) bed, 4.5” (11cm) apart. Weed and thin to 1″ (2.5 cm). When 3″–4″ (7.5–10 cm) tall, cut 1” (2.5 cm) above the soil. Gather a small handful in one hand and cut with using large scissors. Immediately after harvesting, weed the just-cut area so the next cut won’t include weeds. Rake after harvest with a fine leaf rake to remove outer leaves and cut scraps. If you want to make more than one cut, you will need to remove anything that isn’t top quality salad while you can see it. Larger scale operations have harvesting machines.

 

Growing Vegetables in Space — Eat Like an Astronaut

Tokyo bekana in our hoophouse in late December.
Photo Pam Dawling

When I check to see which blog posts are gathering interest, the ones featuring Tokyo bekana are doing well this past year. You might wonder why. It’s because it’s one of the greens being grown on the International Space Station, and most people haven’t heard of it before. I’ve written about Tokyo bekana as a winter hoophouse green here on earth, and as a summer alternative to lettuce in places with hot summers (Virginia, Jamaica, Cuba).

According to an article in The Atlantic, the first plant to grow in space was thale cress, Arabidopsis thaliana, a spindly plant with white flowers, related to mustards, mature 6 weeks after sowing. This was in 1982, on board Salyut, a Russian space station of the era. Thale cress was chosen for practical reasons: a fairly quick life cycle that allows for many analyses in a short time.

Young Outredgeous lettuce in late November. The persistent galinsoga shows that our hoophouse has not yet reached freezing temperatures.
Photo Pam Dawling

The first vegetable grown and eaten on the International Space Station space was Outredgeous red romaine lettuce, in 2015. Bred by Frank Morton of Wild Garden Seed. 64 days to maturity on earth, 33 days in space, with intensely dark red, slightly ruffled leaves forming loose upright heads. “We are an organic seed farm in the Pacific Northwest, established in 1994, owned and operated by Frank and Karen Morton. We are known for farm-original varieties of many salad greens, vegetables, herbs, and flowers.” This is an Open Source Seed Initiative variety. The OSSI pledge: “You have the freedom to use these OSSI-Pledged seeds in any way you choose. In return, you pledge not to restrict others’ use of these seeds or their derivatives by patents or other means, and to include this pledge with any transfer of these seeds or their derivatives.” Read more about OSSI here!

Read Astronauts are about to eat the first food grown in space 2015.  The lettuce was grown for 15 months [? I think several rounds of planting], and the astronauts cleaned the lettuce with citric-acid-based sanitizing wipes before eating it.

Outredgeous lettuce growing in the Veggie module. NASA photo

Space Hydroponics – Veggie 2015

Space gardening has to be hydroponic – there is no soil involved. I am a big proponent of “Keep the Soil in Organic”, as I believe there are nutrients we don’t yet know about, that the plants take up from the soil in the proportions they need. But in space, you can’t do that, soil is way too heavy. If you watched The Martian movie, you saw some hilarious efforts to grow potatoes in “soil”.

In the Space Station is a plant growth system Veg-0, fondly called “Veggie,” a chamber about the size of a carry-on piece of luggage, typically holding six plants. The magenta light bathing the plants in Veggie is the result of a combination of red and blue LED lights. the most efficient way to get good plant growth. Green LEDS were added later so the plants look like edible food rather than strange decorations. Without gravity, plants use other environmental factors, such as light, to orient their growth.

To grow the first food crop, a root mat and six plant “pillows,” each containing ‘Outredgeous’ red romaine lettuce seeds, were put into Veggie. Inside each plant pillow is a growth medium including controlled-release fertilizer and calcined clay as used on baseball fields. This clay increases aeration and helps the plants grow. The plants get about 100 milliliters of water each to start the seeds growing. The pillows distribute water, nutrients and air around the plant root, to prevent the roots from drowning in water or being trapped in air (because of the way fluids in space tend to form bubbles).

Veggie remains on the station permanently as a research platform for other leafy plant experiments (and a source of food and psychological comfort!). The crew does get some fresh fruits and vegetables when a supply ship arrives at the space station, but the quantity is limited and they are soon gone.

See the 2015 article Meals Ready to Eat: Expedition 44 Crew Members Sample Leafy Greens Grown on Space Station

Watch this video to learn more about growing plants in space: https://www.youtube.com/watch?v=YFdwv9yrxD0&feature=youtu.be

For technical information about Veggie, visit here, and also see the 2020 Veggie Fact Sheet

2017-2018 More Space Crops

Next up in 2017 was our friend Tokyo bekana (a frilly Japanese mustard greens).

NASA photo

See the Modern Farmer article from February 2017: The Astronauts on the International Space Station Are About to Harvest Chinese Cabbage (Tokyo bekana)

Tokyo bekana was chosen for its fairly short stature and fast growth. Other contenders included Swiss chard, spinach and beets. The scientists who noted Tokyo bekana’s short stature haven’t seen the healthy 24” (60 cm) ones I just pulled up in our hoophouse today! In our hoophouse climate, it bolts in January, so our plan includes clearing the crop then and sowing spinach for bare-root transplants.

“We conducted a survey of several leafy green vegetables and looked at how the crops grew, how nutritious they were, and how a taste panel felt about them,” Gioia Massa, a scientist on the project, told Modern Farmer in an email. “The ‘Tokyo bekana’ Chinese cabbage variety was rated as the top in growth and the favorite of tasters.”

Waldmanns Dark Green lettuce https://www.johnnyseeds.com

Next the cut-and-come-again harvest method was tried with a few leafy salad greens using: Mizuna mustard, Outredgeous red romaine lettuce and Waldmann’s Green lettuce.

Green mizuna in our hoophouse in November.
Photo Pam Dawling

In some reports the little known Tokyo bekana is called, rather generally, but confusingly, Chinese cabbage or, more specifically, but mistakenly, bok choy, but we growers know the difference! Different sources in English use different names for Asian vegetables. I have a series of blogposts Asian Greens for the Month, which you can find by clicking that Category or using the search box.

————————————————

Asian greens divide into 3 groups:

  1. The turnip family, Brassica rapa, of Asian origin

Some crops are Brassica rapa pekinensis (napa cabbage, michihli, celery cabbage);

Others are Brassica rapa var. chinensis (bok choy): Tokyo bekana is either Brassica rapa var. pekinensis or var. chinensis

Brassica rapa var. japonica (mizuna),

Brassica rapa var. narinosa (tatsoi),

Brassica rapa var. perviridis (komatsuna)

2. The cabbage family, Brassica oleracea, of European origin (Kai-lan, Chinese kale)

3. The Chinese Mustard family, Brassica juncea (Ruby Streaks, Golden Frills, Red Rain)

Returning to 1a Brassica rapa var. pekinensis, there are two types: Wong Bok (Napa cabbage such as Blues, and cylindrical Michihli types) and Celery cabbage (pe tsai), which includes Tokyo bekana and the very similar Maruba Santoh.

  • A fast-growing, looseleaf, non-heading vegetable with light green leaves and white petioles.
  • Mild flavor, tender texture: can be substituted for lettuce
  • Can be ready for harvest in 3–4 weeks after sowing.
  • More heat tolerant than Napa cabbage. Cold tolerant to 25°F (-4°C)
  • Fairly bolt resistant

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Astronaut Serena Auñón-Chancellor harvests red Russian kale and dragoon lettuce from Veggie on Nov. 28, 2018, just in time for Thanksgiving. The crew got to enjoy a mid-afternoon snack with balsamic vinegar, and Auñón-Chancellor reported the lettuce was “delicious!”
Credits: ESA/Alexander Gerst

Advanced Plant Habitat 2018

There are two Veggie units aboard the station, along with a more sophisticated growth chamber, the Advanced Plant Habitat.

The Advanced Plant Habitat (APH) is a growth chamber on the Space Station for plant research like Veggie. It uses LED lights and a porous clay substrate, and a controlled-release “fertilizer” delivering water, nutrients and oxygen to the plant roots.

Unlike Veggie, APH is sealed, and automated with cameras and more than 180 sensors that are in constant interactive contact with a team on the ground at Kennedy, so it doesn’t need day-to-day care from the crew. It has more colors of LED lights than Veggie, and also white, far red and even infrared to allow for nighttime imaging.

APH had its first test run on the space station in Spring 2018 using Arabidopsis thaliana (good old thale cress) and dwarf wheat.

Astronauts have grown eight different types of leafy greens in Veggie at different times. NASA is building up the ingredients for a pick-and-eat salad; or rather, a pick, sanitize and eat salad since there is no way to cook on the station yet.

Dragoon lettuce, Johnny’s Seeds

In 2018, the Space Station grew Dragoon lettuce, a green mini romaine. Compact and uniform. Leaves are thick and have an excellent, crisp texture. Heads are very dense, hold well in the field. Bolting and tipburn tolerant. Resistant to downy mildew, lettuce dieback lettuce mosaic virus and an aphid. For spring, summer, and fall on earth, anytime in space. Suitable for hydroponic systems. By contrast with Outredgeous, Dragoon is Utility Patent granted, meaning other people are prohibited from making, using, or selling the “invention” without authorization.

Another 2018 crop was Red Russian kale

Red Russian kale March 7
Photo Pam Dawling

Recent Space Veggies 2019-2020

In 2019 the Space Station crew cultivated Wasabi mustard (eaten as a microgreen after 10 days of growth, or after 40-45 days as leafy greens) and Extra Dwarf pak choi (Harvest around 2-3″ tall, 30 days after sowing)

Wasabi mustard. Photo Specialty Produce

 

Extra Dwarf pac choi, Kitazawa Seeds


Astronauts Enjoy Space Veggies and Look to the Future of Cosmic Salads Nov 2019

In experiment Veg-04B (see list below) with Veggie, a plant growth unit on the space station, the researchers tested how the quality of light and fertilizer affects the microbial safety, nutritional value and taste of mizuna. Astronauts completed the second of three harvests of this mildly tangy, leafy salad vegetable.

Growing Plants in Space | NASA, January 2020

“A lack of vitamin C was all it took to give sailors scurvy, and vitamin deficiencies can cause a number of other health problems. Simply packing some multi-vitamins will not be enough to keep astronauts healthy as they explore deep space. They will need fresh produce.

Right now on the space station, astronauts receive regular shipments of a wide variety of freeze-dried and prepackaged meals to cover their dietary needs – resupply missions keep them freshly stocked. When crews venture further into space, traveling for months or years without resupply shipments, the vitamins in prepackaged form break down over time, which presents a problem for astronaut health.

NASA is looking at ways to provide astronauts with nutrients in a long-lasting, easily absorbed form—freshly grown fresh fruits and vegetables. The challenge is how to do that in a closed environment without sunlight or Earth’s gravity.”

Microbes in Space

March 2020 Researchers examined the microbial communities growing on the Space Lettuce. A diverse community of microbes lives on typical Earth-grown plants. These may include commensals (which neither harm nor benefit their host), or other microbes. Because microbes can affect the health of plants and those who eat the crops, researchers studied the communities of fungi and bacteria growing on the lettuce.

They identified the 15 most abundant types of microbes on the leaves and 20 in the roots, and found that the identity and range of these microbes was similar to Earth-grown lettuce. This was surprising, given the unique conditions in the Space Station. The scientists had expected to find different microbial communities present.

Happily, none of the bacteria they detected are known to cause disease in humans. Tests confirmed the absence of dangerous bacteria known to occasionally contaminate crops, such as E. coli, Salmonella, and Staphylococcus aureus. The numbers of fungal spores on them was also in the normal range for produce graded as fit for human consumption.

The Next Frontier -Roots in Space

On Nov. 27, 2020, NASA astronaut and Expedition 64 Flight Engineer Kate Rubins checks out radish plants growing for the Plant Habitat-02 experiment that seeks to optimize plant growth in the unique environment of space and evaluate nutrition and taste of the plants.
Credits: NASA

See the latest (December 2020) Astronauts Harvest Radish Crop on International Space Station

Watch Radishes Growing in Space: 27 Days in 10 Seconds

NASA astronaut Kate Rubins harvested radish plants growing in the Advanced Plant Habitat (APH) aboard the International Space Station. She carefully wrapped each of the 20 radish plants in foil, putting them in cold storage for the return trip to Earth in 2021, for further study. Note they didn’t get to eat any.

This is the first time NASA has grown radishes on the orbiting laboratory in the APH. Radishes were chosen because they are well understood by scientists and reach maturity in only 27 days on Earth, under optimal conditions. Radishes are genetically similar to Arabidopsis, thale cress, that researchers have long studied in microgravity.

Radishes are a different kind of crop from the leafy greens that astronauts previously grew on the space station, or dwarf wheat which was the first crop grown in the APH. Root crops require certain triggers to initiate root swelling, and also flowering (not wanted if you want to eat the roots!) Growing a range of crops helps determine which plants can thrive in microgravity and be part of offering variety and nutritional balance for astronauts on long missions.

Unlike previous experiments in NASA’s APH and Veggie, which used clay pillows loaded with a slow-release fertilizer, this trial relies on precise quantities of minerals.

Sophisticated control cameras and more than 180 sensors in the grow chamber let researchers at the Kennedy Space Center monitor growth and regulate moisture levels, temperature, and carbon dioxide concentration.

For the future, NASA hopes to figure out how to grow tomatoes, peppers, beans, and berries in space. And microgreens.

For more generally space diet info, see: Space Food Photos: What Astronauts Eat in Orbit 2013

All Veggie Crop Experiments for Human Consumption 2015-2019

Overall, 15 different types of plants have grown in space in Veggie. Researchers at Kennedy Space Center have tested more than 100 crops on the ground. Click the link to read about them all.

Veggie Crops not for human consumption include more of the same crops, and also zinnias, lentils, mustards and radishes, brome grass, algae and tests of a new type of grow chamber, the Passive Orbital Nutrient Delivery System (PONDS)

Cuban Agroecology Tour: Finca Agroecológica El Paraiso, Viñales

Finca Agroecológica El Paraiso, Viñales. View from the restaurant
Photo Pam Dawling

Cuban Agroecology Tour: Finca Agroecológica El Paraiso, Viñales

Here’s another post from my January 2020 group agroecology trip with Organic Growers’ School to Cuba. I’m posting about this sporadically as I organize my photos and journal.

Day 5 – Saturday January 11 lunch and afternoon

After visiting La Palma, a farm in Pinar del Rio province primarily growing tobacco, and Manolo Tobacco Farm to see cigars made, we went to a farm restaurant called La Finca Agroecologica el Paraiso. Wilfredo is the main farmer and his daughters are the main chefs.

Tidy raised beds and mountain view, Finca Agroecológica El Paraiso, Viñales, Cuba.  Photo Pam Dawling

The farm has 8.9 hectares, with 200 vegetable beds and 80% of the produce is sold through their restaurant, and 20% to hospitals etc (I think that is a legal requirement in Cuba). The restaurant is at the top of the hill, affording beautiful views of the farm.

Part of the vegetable gardens at Finca Agroecológica El Paraiso, Viñales, Cuba. Photo Pam Dawling

We had an exceptionally delicious lunch starting with an anti-stress herbal cocktail. Following that we had squash soup, sweet potatoes, taro, squash, lettuce, cabbage, cucumbers, pickled beans, pickled cucumbers, pork, beef, fish, rice and beans. The most vegetables I ate all week! (Food for tourists tend to be meat focused, although the places we visited could cater for vegetarians and vegans.) We enjoyed flan for dessert.

Outdoor classroom and banana tree at Finca Agroecológica El Paraiso, Viñales, Cuba
Photo Pam Dawling

After lunch we were given a guided tour of Finca Agroecológica El Paraiso. The boxed beds were very tidy, and they are all hand watered with water pumped from the river.

Creole spinach – does anyone recognize this plant? Finca Agroecológica El Paraiso, Viñales, Cuba.  Photo Pam Dawling

Creole spinach – see photo above. I do not know the Latin name for this vegetable, and in my research of hot weather cooking greens, particularly alternatives to spinach, I had not come across this crop before. Leave a comment if you know what it is.

Star garden at Finca Agroecológica El Paraiso, Viñales, Cuba
Photo Pam Dawling

Their “summer lettuce” is Tokyo bekana or maruba santoh. This use of the fast-growing chartreuse tender-leaved Asian green for a salad leaf was one I saw several times in Cuba. I thought I’d invented it! Haha! One summer when our lettuce did not grow according to plan, we served some Tokyo bekana as lettuce, and many people did not notice a difference! (Enough salad dressing will mask any vegetable flavor!) Some farms and restaurants simply call it “lettuce” or “summer lettuce”, some say it is a kind of pak choy, and a few can provide the actual name.

Finca Agroecológica El Paraiso , Viñales, Cuba. Tokyo bekana used as “summer lettuce”. Photo Pam Dawling
Herbs and flowers growing at Finca Agroecológica El Paraiso, Viñales, Cuba.
Photo Pam Dawling

The farm grows aromatic herbs to deter bugs. They use tobacco stem solution to kill pests. Nicotine is a strong generalist poison, which used to be part of the toolkit of organic growers here in the US and in the UK. It has the advantage of being short-lived, so produce can be eaten the day after spraying.

Finca Agroecológica El Paraiso, Viñales, Cuba. Lettuce bed. Photo Pam Dawling

See this video from Franny’s Farmacy. Made by two of my fellow travelers on the OGS Tour.

Finca Agroecológica El Paraiso, Viñales, Cuba – Learning about Sustainability and Organic Farming https://www.youtube.com/watch?v=egnKXHyu8_k

To see more, visit https://vimeo.com/146862523

 

 

Fast Growing Vegetables

Lettuce bed in May.
Photo Wren Vile

Maybe part of your response to Covid-19 is to grow more of your own food, and you are wondering what can bring fastest results. Or maybe you just want to leap into spring and have early harvests. Either way, here is information on some vegetable crops that offer fast returns; ways to get crops to grow faster; ways to get more crops from a small space and some sources for more information.

Vegetable Crops That Offer Fast Returns

In my blog post If Spring is Too Wet in March 2019, I included a paragraph on fast crops.

  • Ready in 30–35 days from sowing are baby kale, mustard greens, collards, radishes, spinach, chard, salad greens (lettuce, endives, chicories) arugula, and winter purslane. Beet greens from thinnings can be cooked and eaten like spinach.
  • Many Asian greens are ready in 40 days or less: Chinese Napa cabbage, Komatsuna, Maruba Santoh, mizuna, pak choy, Senposai, tatsoi, Tokyo Bekana and Yukina Savoy). See my Asian Greens of the Month category of posts. There’s a huge range of attractive varieties, they’re better able to germinate in hot weather than lettuce, and faster growing than lettuce. Most reach baby salad size in 21 days, full size in 40 days. Transplant 4-5 weeks after spring sowing, or direct sow. Nutritious as well as tasty. Flavors vary from mild to peppery; colors cover the spectrum: chartreuse, bright green, dark green and purple. A diversity of crops without a diversity of growing methods! Grow when you normally grow kale. Be aware that Asian greens sown in spring will bolt as soon as the weather heats up, so be ready to harvest a lot at once (if you planted a lot, that is!) You can make Kim Chee.
  • Tatsoi and our August sown catch crop of Tokyo bekana.
    Photo Pam Dawling
  • One summer we sowed Tokyo Bekana as a lettuce substitute. 20 days to baby size, 45 days to a (large) full size. We have also grown this at other times of year, when faced with an empty space we hadn’t planned for.
  • Mizuna and other frilly mustards are very easy to grow, and tolerate cold wet soil to 25°F (-4°C). In addition, they are fairly heat tolerant (well, warm tolerant). Use for baby salads after only 21 days or thin to 8″–12″ (20–30 cm) apart, to grow to maturity in 40 days. Mild flavored ferny leaves add loft in salad mixes and regrow vigorously after cutting.
  • Also ready in 30–35 days are spinach, chard, salad greens (lettuce, endives, chicories) and winter purslane.
  • Ready in 35–45 days are baby carrots (thinnings or the whole row), turnip greens (more thinnings!) endive, corn salad, land cress, sorrel, parsley and chervil. Some of the faster smaller turnip roots can also be ready in 45 days or less.
  • Ready in 60 days are beets, dwarf snap peas, broccoli, collards, kohlrabi, turnips and small fast cabbages (Farao or Early Jersey Wakefield).
  • Also ready in 50-60 days once we are past frosts: zucchini, yellow squash, bush beans, small cucumbers can grow fast.
  • Garlic scallions can be grown over-winter, but will grow quickly in spring. Plant scrappy little garlic cloves you don’t want to cook with in close furrows and wait till the leaves are 7” (18 cm) tall before digging up the plant and preparing like onion scallions (spring onions). Can be eaten raw, but more often cooked. You can also plant whole bulbs without separating the cloves. This is a good use for extra bulbs that are already sprouting in storage.
Our garlic scallions in February. we usually space the rows much closer than this. We’ll start harvesting when they reach 7″ in height.
Photo Pam Dawling
  • See other blog posts in my Cooking Greens for the Month series, and Asian Greens for the Month, as well as Lettuce of the Month
  • Try Eat-All Greens, an idea form Carol Deppe. Patches of carefully chosen cooking greens are sown in a small patch. When it reaches 12″ tall, Carol cuts the top 9″ (23 cm) off for cooking, leaving the tough-stemmed lower part, perhaps for a second cut, or to return to the soil.
Twin Oaks Eat-All Greens on October 19.
Photo Bridget Aleshire
  • Spinach is good for salad or cooking uses. Be aware that the fastest biggest spinach may not last long once it warms up! We have found Acadia and Reflect have good bolt-resistance from outdoor spring sowings.

Fast Varieties of Lettuce and Greens

Bronxe Arrow lettuce.
Photo by Southern Exposure Seed Exchange
  • Grow the right lettuce variety for the conditions. Ones that do well in early spring are often useless here after the end of March, or even mid-February. I like to sow 4 varieties each time (for the attractive harvests, and to reduce the risks if one variety bolts or suffers disease): at least one red and one romaine. We have 5 lettuce seasons, with different varieties:
    • Early Spring (Jan – Mar), 6 sowings
    • Spring (April – May 15), 5 sowings
    • Summer (May 15 – Aug 15), 17 sowings (lots of seed!)
    • Fall (Aug 15 – Sept 7), 9 sowings
    • Winter Sept 8 – 27, 9 sowings
  • Baby lettuce mix can be ready in as little as 21 days from mid-spring to mid-fall. A direct-sown cut-and-come-again crop, the plants regrow and can be harvested more than once in cool seasons. Weed and thin to 1″ (2.5 cm). When 3″–4″ (7.5–10 cm) tall, cut 1” (2.5 cm) above the soil. Gather a small handful in one hand and cut with using large scissors. Immediately after harvesting, weed the just-cut area so the next cut won’t include weeds
  • Leaf lettuce can be harvested by the leaf much sooner than waiting for a whole head of lettuce.
  • Small-leaf lettuces (aka Eazyleaf, One-Cut, Multi-Cut, Multileaf): Johnny’s Salanovas, Osborne’s and High Mowing’s Eazyleaf; Tango, Oscarde, and Panisse (older varieties) too. Full-size plants can be harvested as a head, or harvested with a single cut, 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.
Buckley red oakleaf single-cut multi-leaf lettuce.
Photo High Mowing Seeds
  • Other greens can be sown in close rows for harvesting as salad crops at a height of 3”-4” (7-10 cm). These are called mustard mixes or brassica salad mixes.
  • Many cooking greens can be used as salad crops while plants are small, as you thin the rows of direct-sown crops.

Ways to Get Crops to Grow Faster

  • Sow when the conditions are right. Soil temperature is important. I have a table of soil temperatures in Year-Round Hoophouse on page 208. Vegetable Seed Germination: Optimum soil temperatures for germination and days to emergence, where known.
  • Grow transplants. By starting your plants in a place with close-to-ideal temperatures, rather than direct-seeding when it’s still a bit too chilly outside, you’ll get bigger plants sooner. You’ll also buy time to prepare the soil where you are going to plant out.
  • Find warm sheltered micro-climates, in front of a south-facing wall for example.
  • Make your own warm sheltered micro-climates with rowcover or low tunnels.
  • Take advantage of plastic mulch to warm the soil, for crops that like warmth. Regular black plastic mulch will need to be removed at the end of the growing season, but biodegradable mulch does not. However, if you are taking over part of your yard near your house, I should tell you that you will see shreds of the bioplastic next year. See Setting out biodegradable plastic mulch by hand
Rolling biodegradable plastic mulch by hand
Photo Wren Vile
  • Consider landscape fabric with planting holes burned in, as a reusable alternative to throw-away or biodegradable mulch.
  • Use mixes for salads: Our general salad mix harvesting approach is to mix colors, textures and crop families. I like to balance lettuce of different kinds with chenopods (spinach, baby chard, Bull’s Blood beet leaves) and brassicas (brassica salad mix, baby tatsoi, thinnings of direct-sown brassicas, chopped young leaves of Tokyo bekana, Maruba Santoh or other Asian greens, mizuna, other ferny mustards such as Ruby Streaks, Golden Frills and Scarlet Frills). See Making salad mix
  • Microgreens: See Andrew Mefferd The Greenhouse and Hoophouse Grower’s Handbook.
  • When the weather warms up, consider using shadecloth for heat-sensitive plants, particularly lettuce, but any of the cool weather greens you still have by then.
  • In warm weather, greens and lettuces inside a tipi of pole beans will benefit from the shade.

Ways to Get More Crops from a Small Space

  • With transplants, you can fit more crops into each bed throughout the season, because each crop is occupying the bed for less time than if direct-sown.
  • Transplanting can help you grow more successions of summer crops, as each one needs less time in the garden or field.
  • Grow a vertical crop on a trellis and something short in the space below it. You can even use the same trellis twice, growing tomatoes after peas, for instance.
Spinach and peas in a relay planting scheme.
Photo Twin Oaks Community
  • Relay Planting is a method of growing short crops alongside taller ones. We have often sown peas down the center of a bed of overwintered spinach. As the peas grow tall, we trellis them, and continue harvesting the spinach. When the spinach bolts, we pull it up. This overlap of bed use lets us get more crops from a bed in less time than if we sowed the crops one after another. We have also sowed peanuts down the middle of a bed of lettuce on the same date we transplant the lettuce. We make sure to use vertical romaine lettuces rather than sprawly bibbs or leaf lettuces. We have transplanted okra down the middle of a bed of early cabbage. This does involve breaking off outer leaves of the cabbage if they are about to smother the okra.
  • Sow some slower-maturing crops the same time as you sow the fast ones, so you have food later as well as sooner! Carrots, turnips, cabbages, broccoli, collards, kohlrabi,
  • Sow some multiple-harvest crops to save work later. Greens that are harvested by the leaf, rather than the head, offer good value.

Sources for More Information

  • In High-Yield Vegetable Gardening, Colin McCrate and Brad Halm point out that when planning what to grow, it’s important to consider how long the crop will be in the ground, especially if you have limited space.
  • Cindy Conner in Grow a Sustainable Diet: Planning and Growing to Feed Ourselves and the Earth, leads you through the process of identifying suitable crops for food self-reliance, and provides a worksheet to help you determine Bed Crop Months. For each bed, determine how many months that food crop occupies that bed and so assess the productivity value of one crop compared with another. Short season crops grow to harvest size in 30-60 days, allowing series of crops to be grown in the space, and feeding people quickly. If all your nutrients are to come from your garden, you will need to pay attention to growing enough calories. Otherwise you’ll lack the energy to get to the end of the season!
  • Curtis Stone, in The Urban Farmer, distinguishes between Quick Crops (maturing in 60 days or less) and Steady Crops (slower maturing, perhaps harvested continuously over a period of time). He has designed a Crop Value Rating system based on 5 characteristics. To use this assessment, you look at each characteristic and decide if the particular crop gets a point for that characteristic or not. Then look for the crops with the highest number of points. Spinach gets all 5 points; cherry tomatoes only 3. The smaller your farm, the higher the crops need to score to get chosen. His 5 are:
  1. Shorter days to maturity (fast crops = chance to plant more; give a point for 60 days or less)
  2. High yield per linear foot (best value from the space; a point for1/2 pound/linear foot or more)
  3. Higher price per pound (other factors being equal, higher price = more income; a point for $4 or more per pound)
  4. Long harvest period (= more sales; point for a 4 month minimum)
  5. Popularity (high demand, low market saturation)
  • Steve Solomon in Gardening When it Counts provides tables of vegetable crops by the level of care they require. His Easy List: kale, collards, endives, chicories, spinach, cabbage, Irish potatoes, sweet potatoes, all cucurbits, beets, chard, sweet corn, all legumes, okra, tomatoes (followed by the more difficult eggplant, peppers).
  • See my blog post How to Decide Which Crops to Grow
  • See my article Intercropping: Minimize Your Effort While Maximizing Yields, in the Heirloom Gardener of Spring 2018.
  • Jennifer Poindexter on the Morning Chores Site has a nice simple web post on 16 Fast Growing Vegetables That Will Give You a Harvest Quickly
  • Steve Albert on the Harvest to Table website has a good post on Quick-Growing Vegetable Crops. It includes recommended fast-growing varieties of 29 crops.

Hoophouse Musings, Bugs, Okra, Edible Landscaping Workshops in Maryland

Hoophouse beds in December. This is why we have a hoophouse!
Photo Wren Vile

Winter hoophouse posts in Mother Earth News newsletter

Sowing and Transplanting Winter Crops in a Hoophouse

Grow Great Lettuce in Winter

Winter hoophouse lettuce
Photo Kathryn Simmons

———————————————————

A photo of a Tiny House from Wikipedia

Would you live in a hoophouse?

A reader wrote in:

“I have actually been thinking of building a tiny house and putting it inside a big hoophouse, creating a living area that would include a yard, trees, and gardens – allowing me to snowbird in place in northern New England – but I’m concerned about outgassing, since I’d be there almost 24-7 most days (I work out of my home). Have you done any research on outgassing of hoophouses?”

A Tiny House is generally a residential structure under 400 sq. ft

First off, No I haven’t done any research about hoophouse off-gassing, but I wouldn’t worry about out-gassing from the polyethylene of the hoophouse. Other products  are much closer to your nose: All the materials used to construct, preserve and decorate the house and all the products within the house, such as furniture,  fabrics, soaps, appliances etc.

There are some other things I’d wonder about:

1.      Temperature. When the sun shines, the interior of the hoophouse warms up. When the sun doesn’t shine, it doesn’t. Would you heat the tiny house? You’d have to avoid heating systems that could damage the plants.

2.      Snowfall. When it snows, you need to remove the snow from the roof of the hoophouse. Some snow can be carefully pulled down from the outside. Usually we also walk around inside the hoophouse bouncing a broom on the inside of the plastic to move the snow off. You can’t do that if you have a house in the way.

3.      Humidity. In the winter we grow cold-tolerant hoophouse crops. We are aiming for 65 F (18C). We need fresh air for the plants and to deter fungal diseases. It doesn’t work to keep the hoophouse sealed up and “cozy”!

4.      Strong winds. In hurricanes and gales, hoophouses sometimes collapse or get destroyed. You don’t want to be inside when that happens.

5.      Height. Our hoophouse is less than 14 ft (4 m) at the apex.

In conclusion I’d say it’s better to have a small patio seating area within your hoophouse for suitable sunny days, rather than plan to live inside all the time.
Brassicas in a nematode-fighting hoophouse crop rotation in Hawaii.
Credit Gerry Ross, Kupa’a Farms

Do you value crop rotation in your hoophouse?

A reader in the Pacific Northwest wrote: “This winter I have been re-thinking my crop rotation plan after having some issues (with flea beetle larvae in the soil outsmarting my diligent insect netting of my brassica salad crops). These days I see intensive market gardeners seeming to not worry so much about rotation (i.e. Neversink farm, etc), and yet I’ve always been taught that it is such an important principle to follow. I reviewed your slideshows on crop rotation and also cool crop planning in the greenhouse (which briefly addresses salad brassica rotation with other crops). With how much space I have and the high demand I have for brassicas, for salad mix (mustards) and also the more mainstay cole crops, I had settled on a 2.5 yr between brassica crop rotation (but planting two successions of mustards in the same bed within one year, in the year the bed was in mustards, with a lettuce or other crop breaking up the successions, with the idea that they were very short day and also light feeder crops). Wondering if you think this just doesn’t sound cautious enough, or if this sounds like a reasonable compromise with not having more space to work with (and wanting to satisfy the market demand for brassicas).”

I replied: “Yes, I do think crop rotation is important. I do know some farms seem to have given it up. I think what you are seeing shows one reason why rotation is important. In our hoophouse, we do as you do, allocating brassicas to a space for that winter season and perhaps doing more than one round of brassica crops. Then moving away from brassicas for the next two winters. If doing that doesn’t get rid of the flea beetle problem, and you are being thorough about netting with small-enough mesh netting (sounds like you are, but maybe check the mesh size), then my next step would be spinosad when the flea beetles appear. You can spray the inside of the netting too, and close it quickly. It’s that or a longer rotation, which it sounds like is not financially viable. You could also try farmscaping and/or importing predatory insects (not sure if there are any), Are there beneficial nematodes that attack flea beetle larvae? These are things I don’t know about, but might be worth looking into.”

 

Late sweet corn and sweet potatoes
Credit Ezra Freeman

Sweet Potato fends off bugs

Modern Farmer has this fascinating article about sweet potato plants alerting their neighbors to pest attacks.

Researchers from the Max Planck Institute and the National Taiwan University found that when sweet potato plants are attacked by insects, they emit a bouquet of odors and start production of a protein called sporamin that makes them unappetizing. Neighboring sweet potatoes sense the odors and start their own production of sporamin.


 

A new Tokyo bekana transplant attacked by vegetable weevil larvae October 10
Photo Pam Dawling

Insect damage cause stress-response production of anti-oxidants

In a related piece of news, Agrilife Today from Texas A&M AgriLife Research has found some evidence that wounded plants produce anti-oxidants as a stress response, which may make them healthier for human consumption. Read the report here.

Edible Landscaping with a Permaculture Twist Spring Series

Michael Judd in cooperation with Common Market CO+OP is presenting a combination of hands-on workshops at Long Creek Homestead and evening talks at the Common Market, Frederick Maryland.

Click here for info on Spring Workshops/Talks/Tours

·        Inoculating Mushrooms

·        Fruit Tree Grafting

·        Herb Spirals

·        Creating Growing Beds- Swales and Hugelkultur

·        Edible Landscaping & Straw Bale Home Tour

·  For the Love of PawPaws


 

Fire Ants have reached Toronto

A reader wrote in that the European Fire Ant is now found in Toronto.


“There were two nests of these in my allotment garden 2018.
They actually moved the nest in order to be closer to the zucchini
plants.  Hand on heart: I never had  any cucumber beetles develop past
the instar stage.  The ants did not eat the eggs but they ate the larvae
as soon as they hatched.  Same for potato beetle.  My neighbours had
the best cucumber harvest in history. 
What I’ve read is these Fire Ants kill colonies of native ants.  Summer 2019 I had a Pavement Ant war that went on for days.  Clearly the Fire Ants did not wipe them out.  There are black ants and other smaller red ants
in my garden.  The Fire Ants appear to have moved on for some reason known
only to themselves.   Perhaps they too have enemies.”
“There’s a guy with a Youtube channel who keeps ant colonies.   AntsCanada although he is in the Philippines.  What happened was the feral Pharaoh Ants invaded his colony of Fire ants and killed them.  Pharaoh Ants are much smaller but perhaps that’s what gave them the advantage.   We have Pharaoh ants in Toronto also.   I spend a lot of my time looking at the little critters in my garden.  Like red velvet mites:  there were many in 2016.  Have not seen a single one in two years now. “

Video of Okra Taste Testing

Chris Smith, author of The Whole Okra

Chris Smith, author of  The Whole Okra: Chris has a video of
the taste testing on  Youtube, https://www.youtube.com/watch?v=sAy0pouxlME

Dragonfly Swarms, Mother Earth News, and Heritage Harvest Festival

Dragonfly photo courtesy Staunton News Leader

Swarms of dragonflies are popping up  in Virginia

Leanna Smith, in the Staunton News Leader reported that meteorologists in Ohio had spotted something unexpected on the radar on September 10 — a swarm of migrating dragonflies. The radar maps are impressive! The Common Green Darner dragonflies (Anax junius) were reported swarming in Maryland (Sep 11 evening), New Jersey (Sep 12 nighttime) and Virginia (Sep 11 and Sep 12 morning).

She reported that it is common for dragonflies, especially green darner dragonflies, to migrate south in the fall to find warmer weather, but the swarming is unusual. Ohio State University Entomology Professor Norman Johnson spoke to CNN and said that weather conditions can cause the traveling insects to swarm. In 2018, the Washington Post reported that the migration of green darner is typically unremarkable because the insects rarely travel in packs. Although much is still unknown about the migration of dragonflies, we do know that they are very sensitive to temperature. “Climate warming could really disrupt the presence of this migration,” Colin Studds, an animal ecologist at the University of Maryland Baltimore County, told the Post.

It is fairly common for radar to pick up biological movement, especially around sunrise and sunset when warmer air above us can bend the radar beam toward lower elevations where the movement is occurring, according to meteorologist Chris Michaels.

On September 10, the National Weather Service of Cleveland, Ohio tweeted about the new development.

Clouds of dragonflies.
Photo NWS Cleveland @NWSCLE

Ohio State University entomologist Norman Johnson said the dragonflies are likely Green Darners, which migrate south in the fall. “The insects don’t usually travel in flocks,” he told CNN, “but local weather conditions can cause them to bunch up.” “The big swarms have been recorded a lot over the years, but they’re not regular,” Johnson said.

Details of dragonfly migration are still unclear; researchers have found the winged creatures travel an average of 8 miles per day, but can fly as far as 86 miles.

For up to the minute sightings, see the Migratory Dragonfly Partnership Search page

TOWARD THE UNKNOWN  A common green darner can migrate hundreds of kilometers each year. A new study reveals details of the insects’ annual migration for the first time. Photo Mark Chappell

Susan Milius in Science News reports that Green Darner dragonflies migrate a bit like monarch butterflies, with each annual migratory loop taking multiple generations to complete.

Ecologist Michael Hallworth and colleagues wrote the migration of the common green darner, described December 19, 2018 in Biology Letters, using data on forms of hydrogen in the insects’ wings, plus records of first arrivals spotted by citizen scientists. Citation https://doi.org/10.6084/m9.figshare.c.4320911.v2

“A first generation of insects emerges in the southern United States, Mexico and the Caribbean from about February to May and migrates north. Some of those Green Darners reach New England and the upper Midwest as early as March, says Hallworth, of the Smithsonian Migratory Bird Center headquartered in Washington, DC.

Those spring migrant darners lay eggs in ponds and other quiet waters in the north and eventually die in the region. This second generation migrates south from about July until late October, though they have never seen where they’re heading. Some of these darners fly south in the same year their parents arrived and some the next year, after overwintering as nymphs.

A third generation emerges around November and lives entirely in the south during winter. It’s their offspring that start the cycle again by swarming northward as temperatures warm in the spring. With a wingspan as wide as a hand, they devote their whole lives to flying hundreds of kilometers to repeat a journey their great-grandparents made.

Tracking devices that let researchers record animals’ movements for more than a week or two haven’t been miniaturized enough to help. The smallest still weigh about 0.3 grams, which would just about double a darner’s weight, Hallworth says. So researchers turned to chemical clues in darner tissues. Conservation biologist and study coauthor Kent McFarland succeeded at the delicate diplomacy of persuading museums to break off a pinhead-sized wing tip fragment from specimens spanning 140 years.

Researchers checked 800 museum and live-caught specimens for the proportion of a rare heavy form of hydrogen that occurs naturally. Dragonfly wings pick up their particular mix of hydrogen forms from the water where the aquatic youngsters grow up. Scientists have noticed that a form called hydrogen-2 grows rarer along a gradient from south to north in North America. Looking at a particular wing in the analysis, “I can’t give you a zip code” for a darner, Hallworth says. But he can tell the native southerners from Yankees.

An adult darner, regardless of where it was born, is “a green piece of lightning,” says McFarland, of the Vermont Center for Ecostudies in White River Junction. Darners maneuver fast enough to snap insect prey out of the air around ponds across North America. The front of an adult’s large head is “all eye,” he says, and trying to catch samples for the study was “like hitting a knuckleball.”

Although the darners’ north-south migration story is similar to that of monarch butterflies (Danaus plexippus), there are differences, says evolutionary biologist Hugh Dingle of the University of California, Davis, who has long studied Monarchs, which move northward in the spring in successive generations, instead of one generation sweeping all the way north.

Also, Dingle says, pockets of monarchs can buck the overall scheme. Research suggests that some of the monarchs in the upper Midwest do a whole round trip migration in a single generation. As researchers discover more details about green darners, he predicts, the current basic migration scheme will turn out to have its quirky exceptions, too.”

MASS MIGRATION

At least three generations make up the annual migration of common green darner dragonflies. The first generation emerges in the southern United States, Mexico and the Caribbean starting around February and flies north. There, those insects lay eggs and die, giving rise to second generation that migrates south until late October. (Some in that second generation don’t fly south until the next year, after overwintering as nymphs.) A third generation, hatched in the south, overwinters there before laying eggs that will start the entire process over again. These maps show the emergence origins of adult insects (gray is zero; red is many) captured at sampling locations (black dots).

Diagram by Matthew Dodder, M.T. Hallworth et al/Biology Letters 2018

Geek.com reports that this isn’t the first insect invasion of 2019. In June, the National Weather Service’s radar in San Diego picked up a giant crush of ladybugs about 80 miles across in each direction, over southern California. On June 27, residents of northeastern Ohio found themselves dealing with invasive mayflies, which covered cars, houses, and lampposts across Cleveland, Sandusky, and other areas.

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Mother Earth News Fair

I had a great time at the Mother Earth News Fair at Seven Springs, Pennsylvania. My first workshop, Lettuce Year Round, was on Friday lunchtime and attendees were still arriving. For those who wanted to hear all about it, but missed it, here is the slideshow:

And here is the extended version of Hoophouse Cool Season Crops. It has a lot of bonus material compared to the short workshop I gave last weekend.

Note that all the offers of pdfs of my books to download are scams and nothing to do with me! I cannot stop people posting them. It’s almost enough to stop me posting my slideshows, but I know people appreciate another chance to see the slides.

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Heritage Harvest Festival

This coming weekend, Saturday September 21, I’ll be presenting Winter Gardening: No Tech to High Tech with Ira Wallace at the Heritage Harvest Festival at Monticello in Charlottesville, VA. Ira will talk about outdoor winter gardening, and I’ll talk about hoophouse growing (which isn’t really that high tech!) It’s Saturday, Sept. 21 at 10:30am in the Heritage Tent. Here’s the LINK. The workshop is for gardeners to learn tips on growing cold-hardy vegetables (and not just kale!) out in the open and with varying degrees of protection from rowcovers, low tunnels, coldframes and hoophouses.

Read more about the Heritage Harvest Festival here

Buy tickets in advance here

Weeding rowcovered spinach in winter.
Photo Wren Vile

Potato Research, Mother Earth News Fair PA and Heritage Harvest Festival

Crates of potatoes in our root cellar.
Photo Nina Gentle

Potato Research on Harvest and Storage

Last week I mentioned that while researching potato yield figures, I found an interesting publication, The Potato Association of America, Commercial Potato Production in North America 2010. I’ve been reading that and learning more about potatoes. Here I’m going to focus on harvest and storage, because that’s the bit we’re currently challenged by. I also learned more about planting in hot weather, but that’s for another time.

Potato harvest.
Photo Nina Gentle

In England we planted in spring and harvested in October, waiting for the frost to kill the vines. In Virginia we plant in March and June, harvesting in July and October. We have grown Red Pontiac, Yukon Gold and Kennebec here, mostly. They all seem to be determinate varieties. I only just learned there are determinate (varieties with naturally self-limiting growth, generally “early” varieties) and indeterminate varieties (such as “Russet Nugget,” “Nicola,” “German Butterball” and “Elba”). The distinction is explained in Potato Bag Gardening. Growers using towers, grow bags, and cage systems want indeterminate potatoes, which continue to produce more layers of tubers on the stems as they are progressively covered with more soil. Growers wanting a fast reliable crop in the field mostly choose determinate types, which grow as a bush, then flower and die. The Wild Woolly Web does seem to have some contradictory statements about which varieties are determinate and which indeterminate, and some dedicated container growers make assertions not supported by experienced commercial growers. So Reader Beware! I trust Extension and here’s a link to their Ask an Expert page on potato types, and the University of Maryland Extension Home and Garden Info Center Potatoes.

June-planted potatoes in early September
Photo Kathryn Simmons

Whether the vines die naturally at the end of their lifespan, or they die of disease, or the frost kills them, or you kill them yourself by mowing or flaming, the potatoes will store better if you then wait 2-3 weeks before harvesting. The potato skins thicken up (becoming more resistant to scrapes and bruises) and the potatoes become higher in dry matter. Harvesting is easier if the vines are well dead. We generally bush-hog ours. Decades ago, in England, we had late blight in the middle of the season, and we cut the tops off and made a very smoky bonfire. (I wouldn’t participate in that much air pollution nowadays!) After waiting for a couple of weeks for the late blight spores to die, we dug the potatoes. The idea was to prevent spores getting on the tubers. As I remember, it all worked out OK.

If at all possible, harvest when the soil moisture is 60-80% of field capacity. Not too dry, not too wet. This reduces damage from scraping. If using a digger, don’t set it digging too deep, or too much soil will be damped on the harvested potatoes.

Tuber temperature will also impact bruise and rot susceptibility. Ideally soil temperature will be 45-65F (7-18C).  Because soil temperature lags 3-4 hours behind air temperature rise each day, in cold weather, try to harvest around 6 pm or a bit later. In hot weather, harvest in the morning.

When freshly harvested, potatoes are tender, breathing things. Avoid bruising, which is damage that does not break the skin, by not dropping potatoes more than 6” (15 cm), or throwing them towards a container. Don’t bang them to knock off extra soil.

When harvesting in summer, we stack the crates of potatoes under a big tree overnight to lose some of the field heat before moving them to the root cellar early next morning. Potatoes you take from storage can be no better than the quality of the potatoes you put into storage!

The first part of the storage period is the curing. The potatoes are still actively respiring, so they need a good oxygen supply. Failure to ventilate the cellar enough can lead to Black-heart, where the inner tissue of the potatoes dies and turns black. During the curing period, the skins further toughen up, and cut surfaces and superficial wounds heal over, enabling long term storage. The temperature should be as close to 50-58F (10-14.4C) as you can get. The lower end of the range is best for fresh eating (as opposed to junk food manufacture). Hotter temperatures will promote more rot, and age the potatoes faster, leading to early sprouting. Relative humidity should be 90%, but not 100%! If there is too much condensation, use a fan and open the cellar doors, when temperatures are closest to the goal. Curing takes 10-14 days.

Sorting potatoes .
Photo Wren Vile

We find that a single thorough sorting after 14 days can remove almost all of the storage problems that are going to happen. Not sorting at this point lets rots spread.

After the curing period, the potatoes become more dormant and do not respire so actively. They don’t need as many air changes as during curing, but if the cellar is too warm, you will need to aerate more. The temperature during the storage period should be 40-50F (4.4-10C), and closer to the lower end of the range is best. Constant temperatures or a steady decline is the goal, not dramatic fluctuations. Humidity should still be 90-95%, to keep weight loss to a minimum.

Potatoes have a natural dormancy of 60-130 days (depending on the storage temperature). After that period, they will start to sprout. Some plant extracts, including clove oil, can add 20-30 days storage, and will then need to be reapplied. I do not know anything about this myself, and do wonder how you remove the clove flavor from the potatoes!

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Speaking Events

I have two speaking events coming up in September
Mother Earth News Fair

2019 Mother Earth News Fair Pennsylvania.

September Friday 13- Sunday 15, 2019
Location: Seven Springs Mountain Resort, 777 Waterwheel Dr., Seven Springs, Pa. 15622

I am giving two 60 min workshops

Hoophouse winter lettuce: Green Forest, and Red Salad Bowl, two of our fifteen varieties.
Photo Wren Vile

Lettuce Year-Round on Friday 9/13 12.30-1.30 pm at the Grit Stage

This presentation includes techniques to extend the lettuce season using row covers, cold frames, and hoop houses to provide lettuce harvests in every month of the year. The workshop includes a look at varieties for spring, summer, fall, and winter. Pam Dawling considers the pros and cons of head lettuce, leaf lettuce, baby lettuce mix, and the newer multileaf types. She also provides information on scheduling and growing conditions, including how to persuade lettuce to germinate when it’s too hot.

Cool Season Hoophouse Crops on Saturday 9/14 3.30-4.30 pm at the Building and Energy Stage

Learn how to fill your hoop house with productive food crops in the cool seasons. Pam Dawling discusses suitable crops, cold-hardiness, selecting crops, calculating how much to harvest and how much to plant, crop rotation, mapping, scheduling, seasonal transitions, succession planting, interplanting, and follow-on cropping.

Book-signing at the Bookstore Saturday 4.30-5 pm. Buy new books at the Bookstore and bring your grubby used copies to be signed too!

Demos at New Society Publishers booth, of tomato string-weaving and wigglewire system for fastening hoophouse plastic to framework
Friday 3 -3.30 pm, 4.30-5 pm; Saturday 10-11 am, 1.30-2.30 pm; Sunday 9-10 am. 1-2 pm, 3.30-4 pm

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Heritage Harvest Festival, Monticello, Charlottesville, VA

September Friday and Saturday 21-22, 2019
Buy tickets online
Workshop with Ira Wallace
10:30 – 11:30 am Saturday in the Heritage Tent

Winter Gardening: No Tech to High Tech 

Learn tips on growing cold-hardy vegetables (not only kale!) out in the open and with varying degrees of protection from rowcovers, low tunnels, coldframes and hoophouses (high tunnels). We’ll consider crop choices, planting dates and harvesting so there’s always something to eat for everyone from winter market gardeners to small backyard growers. We’ll explain ways to maximize production with succession planting and follow-on cropping.

 No extra fee for the workshop, included with the price of general admission

Booksigning: SATURDAY, SEPT. 21st, 11:45am – 12:15pm, MONTICELLO SHOP TENT (WEST LAWN). Buy new books at the Bookstore and bring your grubby used copies to be signed too!

December view in our hoophouse, showing lettuce mix and turnips.
Photo Wren Vile

Winter Kill Temperatures of Cold-Hardy Vegetables 2019

Baby greens in a cold frame in January.
Photo Southern Exposure Seed Exchange

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).  We had some extremely cold temperatures of -8°F and -9°F (-22°C and -23°C) in early January 2018. The winter of 2018-2019 was not as brutal. Our lowest temperatures were 6°F (-14°C) 1/31/19, 8°F (-13°C) 12/11/18 and a couple of 11°F (-12°C). This year I found that senposai is  more cold-tolerant than I had thought. otherwise I haven’t got much new news here. My results from other years hold up.

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 Notes

Our double-plastic hoophouse keeps night time temperatures about 8F (4.5C) degrees warmer than outdoors, sometimes 10F (5.5C) 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);

Winter crops snug in our hoophouse in a December snowstorm.
Photo Pam Dawling

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

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.

Hoophouse lettuce Red Tinged Winter and Tango (and senposai) in our hoophouse in December.
Photo Pam Dawling

Outdoor killing temperatures of crops (unprotected unless stated)

35°F (2°C):  Basil.

32°F (0°C):  Bush beans, 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, chicory roots for chicons, and hearts, Chinese Napa cabbage (Blues), dill (Fernleaf), endive (Escarole more frost-hardy than Frisée), 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.

22°F (-6°C): Some arugula (some varieties are hardier), Bright Lights chard, large leaves of lettuce (protected hearts and small plants will survive colder temperatures), rhubarb stems and leaves.

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), celeriac, celtuce (stem lettuce), some head lettuce, some mustards/Asian greens (Tendergreen, Tyfon Holland greens), flat leaf parsley, 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).

Closing rowcovers after a winter spinach harvest.
Photo Wren Vile

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, endive, 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) if not covered, broad leaf sorrel, most covered turnips, winter cress.

12°F (-11°C): Some beets (Cylindra,), some broccoli, 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, most fall or summer varieties of leeks (Lincoln, King Richard), large tops of potato onions, covered rutabagas, some turnips (Purple Top).

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

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, 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.

Garlic shoots poking through the mulch in January.
Photo Pam Dawling

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 savoyed 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).

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

Vates kale with a freeze-killed center January 19 2018. Photo Pam Dawling

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

Many of our Vates kale plants survived those cold temperatures Photo Pam Dawling

-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).

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

March 2020 Update: Click the link

Hoophouses I visited this month

In early November, during the Carolina Farm Stewardship conference I went on the afternoon bus tour to see 10 high tunnels and how they’re used for season extension,  irrigation, disease control, pest protection, and trellising. Red Hawk Farm grows salads and greens year-round in six high tunnels (more under construction!), and sells primarily to local grocery stores and restaurants.  Funny Girl Farm grows produce year-round for its popular farmstand and CSA, with four high tunnels and a greenhouse.They were focusing on the sweet potato harvest outdoors when we visited.

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

At Red Hawk Farm I was astounded to see this whole hoophouse planted wall-to-wall with multileaf lettuces. No aisles! The farmer Brett Evans plans to harvest with a walk-behind motorized salad harvester machine that makes a 4 ft wide cut. Then he’ll leave the lettuces to regrow. He uses the paperpot transplanter  which I mentioned last week. Here are the starts growing in their propagation house.

Lettuce starts in paperpots at Red Hawk Farm.
Photo Pam Dawling

They still had peppers bearing well in one high tunnel

Early November pepper harvest at Red Hawk Farm.
Photo Pam Dawling

Another interesting feature was the opening roof vent, which I had not seen in operation on a hoophouse before.

Opening roof vent on a hoophouse at Red Hawk Farm.
Photo Pam Dawling

And this past week, I went to Potomac Vegetable Farms in northern Virginia for a talk with Future Harvest CASA members, and a tour of the hoophouses used there led by farmer Zach Lester.  I was interested in seeing the success he is having with caterpillar tunnels. These are smaller tunnels with a single layer of plastic, held in place by ropes, as you see in the photo below. They can be temporary or short-term, and Zach showed us one which is a “swing house” with two sites side by side, sharing one row of ground posts, and having just one row to move each time. Another way to deal with crop rotations and reduce the chances of pests and diseases!

Caterpillar tunnel at Potomac Vegetable Farms.
Photo Pam Dawling

At the ends, the plastic is gathered up and tied to well-anchored stakes, as you can see here.

How the ends of caterpillar tunnels are gathered and fastened to stakes.
Photo Pam Dawling

Zach got these frames custom made by Nolts. They have taller sidewalls than many models. He is also a firm believer in having a ridgepole in caterpillar tunnels, to reduce the likelihood of collapse with snow or high winds. As you can see here, they had some snow already.

Potomac Vegetable Farms caterpillar tunnel showing rolled up side.
Photo Pam Dawling

At both these farms, I learned the technique of laying landscape fabric along the side walls to reduce weed growth. You can burn holes in the landscape fabric where the ground posts go through, and it will keep the weeds away for a long time. I wish I’d known that technique when we put up our hoophouse. We have to hand weed, and in some places we have wiregrass (Bermuda grass) which has grown under the baseboards and even between the boards where there are joins.


Lastly, I have of course visited our own hoophouse at Twin Oaks, and have written a post for Mother Earth News Organic Gardening on Dealing with Snow on Your Hoophouse. So if it’s snowing where you are, you can click on the link to read about that.