Vegetable Growing Tips from Conferences, Winter 2023-2024. Part 1 CFSA

 

A Spacemaster cucumber plant in our hoophouse on April 23.
Photo Pam Dawling

I love learning new things and getting tips for improving our vegetable production. My events page tells you about recent and upcoming conferences. After I get home from conferences, I usually need to dive back into work, and am in danger of ignoring things I learned. Hence this blogpost. I’ll pass tips on, and extract the gems from my hand-written notes, making it more likely I’ll do something useful with them!

CFSA SAC 2023 banner

In November 2023 I took part in the Carolina Farm Stewardship Conference. I went to an engaging workshop called On-Farm Cover Crops Research in the Carolinas by Justin Duncan from NCAT/ATTRA, Jason Lindsay from the Southeastern African American Farmers’ Organic Network, and Steve McAllan, a last-minute substitute. I’ve got a blogpost brewing about native cover crops in vegetable production, so I’ll save the content for that post. Patrick Johnson also gave a presentation on native cover crops, which I’ll include more about in the promised post.

https://www.youtube.com/c/clem’sorganicgardens

I also participated in a workshop on Advanced Organic Weed Management for Vegetable Growers, given by Clem Swift of Clem’s Organic Gardens, from Pisgah Forest, NC, where they have 8 acres in field production of vegetables. I hadn’t realized the workshop was mostly machinery-focused, but I learned actionable tips anyway! I watched his video on potato planting, cultivation and harvest, which is similar to the way we grow potatoes. I learned a way of covering the edges of plastic mulch by walking backwards with one foot on the plastic to tension it, hoeing soil up onto the plastic. That sounds easier than our method using shovels, but sounds like it does require looser soil than we sometimes have where we use plastic. Clem has a well-organized system of first removing perennial weeds, then cultivating early and often to deal with annual weeds, including using a double-wheeled wheelhoe with a scuffle on either side of the row. Perhaps like one of these:

Double-wheeled double-scuffle wheelhoe. Hoss Tools
Double-wheel double-sweeps wheelhoe. Sweeps available as a conversion kit from Earth Tools.

Johnny’s Selected Seeds has a Wheelhoe Selection Guide in their Tool Library

Next I attended Precise Nutrient Management for Small-Scale Farms by Kyle Montgomery of Advancing Eco Agriculture. Kyle’s goal was to help us answer the question: How could marketable yields be significantly increased with minor changes to a fertility program? Plants have different nutrient requirements at different stages of growth. Sap analysis can show what the plant is taking out of the soil. In each 24 hour period, we want all soluble nitrogen to be converted to stable forms. This was something new for me to think about. I didn’t bring away anything specific to work on.

South Wind slicing cucumber.
Photo Common Wealth Seed Growers

High Tunnel Cucumber Production by Joe Rowland, CFSA’s Organic Initiatives Coordinator, covered preliminary findings from year one of CFSA’s SARE-funded organic high tunnel cucumber project. They trialed 6 varieties of cucumbers grown on 2 different trellis types (drop lines vs Hortanova netting) to compare disease occurrence and severity and marketable yield. Three participating farms replicated the trial to see what works best throughout the region.

Excelsior pickling cucumber. Photo Johnny’s Seeds

Their standout varieties were Itachi, an Asian white slicer (low yield but good disease resistance), and Excelsior pickler (highest yield).

Itachi white Asian slicing cucumber. Johnny’s Seeds

Poniente (a parthenocarpic European slicer) had the most disease of the 6 in the trial; Shintokiwa had the least disease, but was a slow producer, with low yields. The dropline system uses a single leader, more clips, more pruning and twirling than the Hortanova, where two “rows” could be made per bed, training two leaders from each plant in a V. This gave good airflow, slowed down the height-increase compared to single leader plants, and enabled herbs to be intercropped. We grow a succession of five or six plantings of cucumber, mostly outdoors, sprawled on the ground. Only for the early crop does it seem worthwhile to us to grow them in the hoophouse. But I’ve no idea how our yield compares with trained high    tunnel cukes, and perhaps measuring it would lead me to a different plan!

 Poniente cucumber. Territorial Seeds. Note trellis.
Shintokiwa cucumber High Mowing Seeds

Cover Crops for February: Oats if you have a 6–10 week gap

Oats Cover Crop, Steve Groff farm, Holtwood PA. SARE Soil Health Resources

Cover Crops for February: Oats if you have a 610 week gap

In February, you’ll hopefully have made your crop plans and maps. Perhaps you’ve discovered some beds with no winter cover crop, that you are not using for early spring crops? Those winter annual weeds, chickweed, dead nettle and henbit, will shed lots of seeds if you let them.

If food crops were harvested too late to sow any winter cover crops, in early spring you will be looking at weeds, or “spontaneous vegetation” as I’ve heard them euphemistically called. The first year I gardened in Virginia I had lots of beds in April with purple flowers (henbit, purple dead nettle, some ground ivy) and I couldn’t think what to do – I didn’t need those beds for a few more weeks, so I wasn’t ready to till them. Oh, so wrong! I had squandered an opportunity to improve the soil as well as deal with weed seeds.

Now, when we have the crop plans made, we tag any beds that won’t be used for six weeks or more, till in the weeds and sow oats. In February or March here, with a last frost date of April 30, six weeks is just enough time here to make enough growth to out-compete the weeds and add to the organic matter in the soil.

Examples of crops in our gardens that occupy beds too late for us to sow winter cover crops include late cabbages, the last lettuce, leeks and fall Asian greens. Examples of late spring crops the next year include eggplants, peppers, tomatoes, edamame and chard. In some cases, we might even have no food crop planned until August or the beginning of September.

Six–ten weeks (depending on your climate) is long enough in early spring to get worthwhile growth from oats before prepping for the food crop.

Once we get to March 31 here, it is too late in the year for oats (they will quickly head up after making very little growth) and too soon to rely on frost-tender cover crops. See the section below on Stale Seedbed Technique.

Oats Cover Crops Steve Groff farm, Holtwood PA SARE Soil Health Resources

I wrote about oats as a winter-killed cover crop in August.

Will oats work as an early spring cover crop for you?

Large oat plants will be killed by three nights at 20°F ((–7°C) or by a single plummet to 6°F ((–14°C). Oats seedlings die at 17°F (–8°C). Consider your likely nighttime low temperatures during the period in question, and how likely your seedlings are to die. Oat cover crops of a medium size die around 10°F (–12°C). If they die after growing to adolescent size, no worries – just till them in before planting your next crop.

The minimum soil temperature for germination of oats is 38°F (3°C), and the time required to grow to a worthwhile height in cool weather is 6–10 weeks.

If you are in zone 8 or warmer, oats will not winter-kill, and can be grown in winter too – they may not reliably mow-kill, but are relatively easy to incorporate.

Oat plant and seeds. SARE

Pros and cons of oats as a cover crop

Like most cover crops, oats add biomass and nutrients, increase the biological activity of the soil, smother weeds, reduce soil erosion (their fibrous roots anchor the soil) and absorb and store rainfall. Oats are easy to establish, are fast-growing and particularly good at shading out germinating weed seeds and at salvaging any nutrients (especially nitrogen) left from the previous crop and making them available to the following crop.

In early spring you won’t get as much biomass as from a fall oat cover crop, when you can get. as much as 2000–4000lbs per acre (2240–4480 kg/ha. Certainly not enough to be a no-till cover crop for your next food crop. Oats provide some allelopathic effect (producing biochemicals which inhibit the growth of other plants) although less than winter rye. Like most plants, oats form arbuscular mycorrhizal associations (fungi penetrate the plant’s cell walls and help capture nutrients from the soil) – a mutually beneficial relationship, although probably not a big feature when conditions are cold.

Oats are not as good as some other cover crops at breaking up compacted subsoil, although they do loosen the upper layers of topsoil nicely. (Just where you are going to sow.) Oats do not add nitrogen, and unlike flowering cover crops, they do not attract beneficial insects (assuming they are turned under or mowed before heading up and shedding pollen).

Common Oats. Buy Organic and avoid GMO canola seed inclusions

Buying oats, sowing rates

We used to buy “horse oats” (feed oats) locally and not worry about organically certified seed. But I noticed canola sprouting along with the oats, and I don’t want GMO canola going feral in our gardens! We plan ahead and order extra Organic spring oats in summer when making our big cover crop seed order.

Oats will grow in soils with a pH range of 4.5–7.5, and even do OK in soils without great fertility. They have some tolerance to flooding, but not much to heat or drought (although more than rye).

The sowing rate for drilled oats alone is 80–100lbs/ac (90–123 kg/ha). The broadcast rate is 110–140lbs/ac (123–155kg/ha). On a small scale, this is 4–6 oz/100 sq ft (12–20gm/sq m). Aim to cover the seed to a depth of about 1″ (2.5 cm).

Oats grow to a height of 2–4 feet (0.6–1.2 m) if not killed before then.

Stale seedbed technique and tarping

If you have less than 8 weeks until you need to plant the food crop, you are better off mowing when you can, or weed whipping, to prevent weeds seeding.

Tarping beds to kill weeds.
Photo Cornell Small Farms Unit

You could mow and tarp. I don’t yet have much experience of tarping, but there are good directions in The Lean Micro-Farm and The Market Gardener. There are also online videos. The basic idea is to mow the bed, cover it with a black plastic silage tarp, weight down the edges to get good soil contact and stop the tarp blowing away, and wait till the plant matter has disintegrated, or until you need to use the bed. This will take several weeks in cold weather, (although only a few weeks in summer). If you have a late-finishing fall crop, you could mow and tarp as soon as the crop is finished, and leave the bed tarped until spring. Weeds germinate under the tarp, but then die without light.

For a stale seedbed technique without tarps, you could mow, till several weeks before planting, water (if it doesn’t rain) to germinate weeds, and hoe off those weeds once a week. This can really help reduce the weed seedbank in the soil. It is particularly useful before sowing small seeds of slow-growing crops, such as carrots.

What not to sow in short gaps in early spring

Other quick cover crops, like buckwheat and soybeans, are not at all frost-hardy, so wait until after your last frost date to sow those.

In early spring, the air and the soil are cold, and sowing a fast-growing vegetable crop will not be successful with a gap of less than eight weeks. Crops take too long to grow at this time of year.

 Spring gaps longer than eight weeks

If you have more than eight weeks you could try those fast-growing vegetables: kale, spinach, Tokyo bekana, radishes, chard, lots of salad crops, senposai, mizuna, tatsoi, land cress. Or try Eat-All Greens, an idea from Carol Deppe. Patches of carefully chosen cooking greens are sown in a small patch. When it reaches 12″ (30 cm) 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.

Young spinach seedlings.
Photo Pam Dawling

Undersowing oats in spring

Another way we have used oats in spring is between rows of peas (grown on the flat, not in beds). We sowed the oats the same day as the peas, and lightly tilled the oats in. We mowed the oats as needed during the pea training and harvest period to make access easy. This reduced the number of weeds, and we quite liked the “lawn” underfoot!

Green fallow (Full year cover crops)

If you have a bed with no crop planned for the whole season, you could grow a Green Fallow. You can plant long-term cover crops to replenish the soil. Start with oats or one of the more cold-hardy grasses, and once we get to warm weather, after the frosts, till that in (or mow if it mow-kills) and sow warm weather cover crops.

Reasons not to do no-till food crops in spring

Untilled soil in spring is colder than tilled soil, and growth of anything you plant in it will be slower, and harvests delayed. You could consider broccoli or cabbage, perhaps, but not warmth-loving crops. You may get more slugs and/or more fungal diseases with no-till. The cover crop could try to regrow, or you could get some weeds anyway.

Also, if you are planting by hand, transplanting into untilled soil is harder work than planting into loose tilled soil. Hand-sowing into untilled soil is tricky – winter snow and ice can leave quite compacted soil. If the notion of organic no-till appeals to you, experiment on a small-scale the first year. Reduced tillage is another option. Till out narrow strips in the oats for your plantings of large food crops normally grown on a wide row-spacing.

Using a push seeder for cover crops

EarthWay push seeder.
Photo from EarthWay

You can drill cover crop seeds using a push seeder. See VABF Using Manually-Operated Seeders for Precision Cover Crop Plantings on the Small Farm. Don’t worry if the seed ends up deeper than ideal. It will still germinate.

 

Cover Crop Planning

My book Sustainable Market Farming has a chapter on cover crops and 9 pages of charts about particular options.

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book or download it as a free PDF from SARE.

Cover Crops in January: The Big Picture

Winter rye and crimson clover cover crop
Photo by McCune Porter

Since May 2023 I have written a post at the beginning of each month about cover crops. In most parts of the US,  January is too late to plant any cover crops, and too early to terminate any  in preparation for sowing(except winter-killed ones!). This is a great time to ponder your cover crop strategies for the coming year, and perhaps plan some changes or tweaks.

I found a great treasure trove of cover crops resources from SARE (Sustainable Agriculture Research and Education). The Resources and Learning tab led me to the Cover Crops Topic and the four page publication Cover Crops for Sustainable Crop Rotations.  

My search for slideshows didn’t immediately turn up the collection I had saved previously, but there is plenty there to usefully inspire you on a rainy day, when you’re all caught up on the accounting and the tool repairs! Or even sooner.

Here’s a compilation of slides I made from SARE’s materials. There are slides on reasons to grow cover crops, some beautiful photos of some good “starter” cover crops, factors to consider when choosing cover crops, information of planting equipment options and opportunities, and several slides of further resources.

Sit back and enjoy the show!

SARE Cover Crops Materials Digest

 

I can also give you to the most recent version I have of my own cover crops slideshow

Cover Crops for Vegetable Growers 2023 60 mins

 

Cover of Managing Cover Crops Profitably book from SARE

Happy New Year , and all the best for a great 2024 growing season!

Cover Crops for December: Planning for Next Year

Our asparagus patch mulched for the winter.
Photo Kathryn Simmons

 

Keeping the Soil Covered all Winter

Don’t plant cover crops in December, unless you live in a warmer place then Zone 7a. Weeds will be our cover crop for the next few months! You can mow the weeds anytime you see lots of flowers and seed heads. For us, it’s usually one mowing in November, then no more until early February.

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.

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 micro-organisms thrive when they have active plants to cooperate with, exchanging nutrients).

If you are less than 3 weeks past your first frost, see my post Cover Crops for November. It is still worthwhile to sow a few cover crops up to three weeks past your average first frost. 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. Two or three weeks past your first frost, you could sow winter rye. Winter rye is hardier than any other cover crop and can take later planting dates. If you don’t have winter rye, don’t till! Leave the weeds.

You could mow and tarp, to kill the weeds before spring. I’m not sure what the soil life thinks about that, though!

If you don’t have weeds, but only almost bare soil, and it’s too late to sow cover crops, find some kind of organic mulch. Cardboard weighted down with bricks or rocks is much better than nothing.

Be prepared to act early in spring, so you don’t get weed seeds. You could mow 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.

This rye cover crop is still small in early March, but will soon make rapid growth.
Photo Pam Dawling

Plan Cover Crops for Next Year

Our other cover crop related task is planning for next year, and ordering seeds. See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops.

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 average first frost date, and your winter-hardiness zone (the lowest temperature your garden is likely to encounter).

Create a crop rotation for vegetables that includes good cover crops

If you haven’t yet made a plan for next year’s cover crops, a good time to do it is when planning the crop rotation for your vegetables. You can tweak your plan to maximize your cover crop opportunities.

Here’s 5 steps of cover crop planning:

  1. Identify your opportunities for cover crops (When, how long, how warm, crops before and after)
  2. Clarify your cover crop goals for each opportunity (check list of benefits above)
  3. Shortlist suitable cover crops for each situation (consult books and charts)
  4. Make a decision from among the options to match your main goals and some secondary goals
  5. Record your decisions and results, and review for possible changes next year.
Sunn hemp cover crop at Nourishing Acres, North Carolina.
Photo Pam Dawling
Step 1 – Cover crop opportunities
  • In fall after food crops, for the whole winter – the easiest place to start
  • In late winter or early spring, if the area will not be planted with a food crop for 6 weeks or more.
  • In spring, summer or fall, whenever you have 4 weeks or more between one vegetable crop and a later one
  • Undersowing at last cultivation (usually 4 weeks after planting the vegetable crop)
  • To replace a crop failure, smother weeds, make use of the compost you provided for the failed crop.
  • Year-round cover crops (green fallow) if you have a space you will not be using for vegetables in the coming year.
Step 2 – For each opportunity, clarify your cover crop goals

Which cover crop benefits are your main priorities and your secondary goals at that site?

  • Smother weeds, prevent them growing and seeding
  • Add organic matter and nutrients
  • Increase the biological activity in the soil
  • Reduce erosion by using actively growing roots to anchor the soil
  • Improve the tilth of the soil and the sub-soil structure
  • Improve soil drainage
  • Improve the soil’s ability to absorb, hold water
  • Salvage leftover nutrients
  • Fix nitrogen to feed the next crop
  • Attract beneficial insects
  • Bio-fumigation for pest or weed control
Step 3 – Choose cover crops matching your goals
  • Smother weeds: sorghum-sudangrass, pearl millet, winter rye, wheat, barley, oats, buckwheat, brassicas, lupins, red clover, subterranean clover, berseem clover, soybeans, southern peas
  • Add organic matter, improve the soil’s ability to absorb, hold water: bulky grasses and legumes, sorghum-sudangrass, millets, winter rye, velvetbean, southern peas, sweetclover, sunn hemp (Crotalaria)
  • Increase the biological activity in the soil – use varied mixes
  • Reduce erosion: (good roots) grasses especially rye, barley, oats; also sweetclover, southern peas, sub clover,
  • Improve the tilth of the soil, the sub-soil structure, soil drainage: sorghum-sudangrass, sunflower, daikon, sweetclover, crimson clover, alfalfa, lupins, southern peas, forage radish, sugar-beet or forage-beet
  • Scavenge leftover nutrients: (non-leguminous cover crops) grasses, brassicas (pest and rotation problems), annual ryegrass (danger of it becoming a weed)
  • Fix nitrogen: (legumes) clovers, vetches, peas, southern peas, soybeans, lentils, sunn hemp.
  • Attract beneficial insects: (flowers) buckwheat, peas, beans, clovers, brassicas, phacelia, sunn hemp
  • Pest control: rye, brassicas, sorghum-sudan, sunn hemp, white lupins, sesame.
  • Kill nematodes: Pacific Gold mustard, white lupins, Iron and Clay southern peas, OP French marigolds, sesame
Iron and Clay southern peas flowering in September. Photo Pam Dawling
Step 4 – Choose cover crops for the fall and for the summer

Work back from your farm’s first frost date, to see what options you have in the fall. In the summer work with the length of time that plot has before you need it for another food crop.

Here’s my 7 steps of crop planning:

  1. Figure out how much area is needed for each major crop (the ones needing the largest amount of space).
  2. Measure and map the land available
  3. Divide into equal plots big enough for any one of your major crops
  4. Group compatible crops together to fill out each plot not yet housing a major crop
  5. Set a good sequence, maximizing cover crop opportunities
  6. Include best possible cover crops at every opportunity
  7. Try it for one year, then make improvements

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

Cover Crops for November: Winter Rye and Austrian Winter Peas

Cover Crops for November: Winter Rye (with Austrian Winter Peas early in November)

Winter rye headed up. Mow or turn it under very soon! Don’t let it shed seed.
Photo Pam Dawling

The first half of November is the last chance to sow winter cover crops in central Virginia

Our average first frost is October 14-20. If yours is later, see my post Cover Crops for October. It is still worthwhile to sow a few cover crops up to three weeks past your average first frost, and I’ll tell you about those, with ideas on what to do if your climate is past that point.

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.

See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops and my slideshow Cover Crops for Vegetable Growers.

Last Chance Cover Crops in November: Rye

Rye grows impressive roots that improve the soil. Kauffman Seeds

Winter rye can still be sown in the mid-Atlantic in the first half of November. Winter rye is the cereal grain rye, not ryegrass. Ryegrass comes in annual and perennial forms, but neither is a good winter cover crop here. They don’t produce as much biomass as cereal rye, and can become weeds in our climate.

Winter rye is hardier than any other cover crop and can take later planting dates. Some people do sow winter wheat in early November rather than winter rye, so if you don’t have rye seed, use wheat. It can be tricky to have the cover crop seed you want, without risking buying more than you need. Sometimes it pays to use what you already have, as it may not give good germination if saved over to next fall.

Winter rye has an allelopathic effect (inhibition of germination) on small seeds, that lasts three weeks or more after rye is turned under. This means you will need to be fairly confident that the weather will allow you to till the rye in with three weeks to go before sowing carrots, spinach or other spring crops with small seeds. Transplants are not affected in the same way. If necessary, reconfigure your crop rotation plan over the winter. Plan for the next food crops after winter rye to be ones planted after late April, such as late corn plantings, winter squash, transplanted watermelon, sweet potatoes, tomatoes, peppers, June-planted potatoes, fall brassicas, and second plantings of summer squash, cucumbers, beans.

A field of winter rye with a strip of crimson clover in early May.
Photo Bridget Aleshire

Other key features of winter rye cover crop

  • Rye grows 5′-7′ (1.5-2.1 m) tall.
  • Mow-kills at flowering, but not earlier.
  • Suppresses weeds (especially lambsquarters, redroot pigweed, ragweed).
  • Adds lots of organic matter if grown to full size.
  • Improves the soil’s ability to absorb and store water.
  • The roots hold the soil together and greatly reduce erosion.
  • Can be used to scavenge nutrients left over from a previous legume crop or to hold onto nutrients applied for a crop that failed.
  • Sow from 14 days before to 28 days after first fall frost.
  • Don’t sow before September in zone 7 – it may set seed.
  • Rye makes little growth in mid-winter, but very good growth once spring arrives.
  • Rye can be sown in the spring, although when incorporated, oats break down quicker.
  • Can be undersown in sweet corn or in fall brassicas in early September, and left as a winter cover crop.
Cover crop of rye and winter peas with flowering crimson clover. Photo Bridget Aleshire.

Include Austrian Winter Peas if possible in the first week of November

See my September post for more about the benefits of including legumes with winter cover crops grasses. Also how to inoculate legume seeds with the nitrogen-fixing bacteria. Austrian winter peas can be sown later than other legumes. See my October post for more about those. See Working with the time you have left for options if you are in another climate zone.

A key to success with legumes is to sow early enough in fall to establish before winter halts growth, and to plan not to need that plot next year until flowering time for that legume. Austrian winter peas bloom here at the end of April (about a week later than crimson clover, and a week earlier than hairy vetch). (If you have a legume that doesn’t reach flowering, you get less nitrogen for your money, and will need to add some compost or other source for the following food crop.) Suitable crops for following Austrian winter peas are ones planted after May 1: winter squash, melons, sweet potatoes, tomatoes, peppers, middle sowings of sweet corn, June-planted potatoes. This is pretty much the same list as crops that can be planted after winter rye.

Austrian winter peas
Photo https://www.uaex.edu

October 15 (our average frost date) is our clover/peas watershed (legume-shed?). Before that date we use crimson clover; after it (until 11/8, 3 weeks after our average frost date) we sow Austrian Winter Peas, along with winter rye or winter wheat.

Austrian winter peas winter-kill in zone 6, but are hardy in zone 7. Hardy to 0°F (-18°C). Sow Austrian winter peas at least 35 days before first hard freeze (25°F/-4°C) – in zone 7, that’s a 50% chance on 11/8. See Weatherspark.com for info on your location, or Dave’s Garden.

Last Chance cover crop

In the second week of November, we sow winter rye alone as our last chance cover crop. It is too late for any legumes.

Grain seed will store OK for the next year, but peas and beans really lose viability fast. If you still have Austrian winter pea seed from last year, I’d say throw it in this November rather than keep it for a third year, even if you are past the usual date. Germination rate goes down to 50% after a couple of years, and the plants won’t be sturdy.

Barbara Pleasant tells us two other ways cover crops can improve soil: Rhizodeposition and bio-drilling.

Rhizodeposition is a process whereby plants release sugars and other substances through their roots. The root tips host colonies of helpful microorganisms that go deeper as the roots grow deeper.  For rye, this depth can reach 6 feet (2 m)!

Bio-drilling is what happens when cover crop roots “drill” into compacted subsoil. Oilseed and daikon radishes are cover crops famous for this action. The roots push deep into tight subsoil. Bio-drilling also happens when deeply rooted cover crops penetrate the subsoil and then die. With winter rye this can happen when the headed-up rye is mowed close to the ground in spring, or the rye is tilled into the top soil, severing the roots below till level. The next crop can follow the root channels made by the cover crop. This gives access to nutrients (including dead roots and microbes) left behind by the cover crop.

How to protect the soil over the winter if it is too late for cover crops

Carrot harvest cart. Our Danvers carrots have plenty of sturdy leaves to protect the soil over winter. Photo Mari Korsbrekke

Sowing cover crops too late means you don’t get enough growth in the fall, and the soil is not adequately protected from erosion or from weed growth over the winter. Try really hard not to leave bare soil over the winter.

If it’s too late to sow cover crops, but you do have a healthy growth of weeds, mow them at the beginning of November and then leave everything alone until early spring. The weed roots will hold the soil together and the above-ground growth will protect the soil from heavy rain. Having live plants will provide food for the microbial life in the soil.

If you don’t have weeds, but only almost bare soil, and it’s too late to sow cover crops, find some kind of organic mulch to cover the soil. When we harvest our storage carrots in November, we return the cut tops to the soil surface. Another seasonal option is tree leaves (sometimes conveniently left in bags by the curb). Best to ask the “owners” before lifting them. Other ideas include straw or hay. Woodchips or sawdust will work for winter protection, but don’t till them in when spring arrives. Rake them off and compost them nearby. If turned under, they use up a lot of nitrogen decomposing, and your crops will be starved.

More resources on cover crops

My book Sustainable Market Farming has a chapter on cover crops and many pages of charts about particular options.

Cover of Managing Cover Crops Profitably book from SARE

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book for $19 or download it as a free PDF from SARE.

Cover Crops for October: Winter Wheat and Austrian Winter Peas

Austrian Winter Peas

Focus Cover Crops for October: Winter Wheat and Austrian Winter Peas

In August I wrote about cover crops such as millets, southern peas, buckwheat which are frost-killed. For most of us in the mid-Atlantic, it’s too late for those.

October is too late to sow winter-killed cover crops in central Virginia

Our average first frost is October 14-20. If yours is later, and you still have 40-60 days to your average first frost, you can still 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, the cut-off date for oats is September 15 if we really push it. Sowing too late means you don’t get enough growth in the fall, and the soil is not adequately protected from erosion or from weed growth.

Oats winterkill completely at 6°F (-17°C) or three nights at 20°F (-7°C. Fall-sown barley (Hordeum vulgare), grows even faster than oats, and dies at 17°F (-8°C).

There are still three weeks here when it is worthwhile to sow cover crops (up to a month past first frost), and I’m going to write about those here.

See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops and my slideshow Cover Crops for Vegetable Growers. Oats, barley, wheat and rye sown too early can head up and seed before you get to winter, making them less useful, and more of a weed problem. Once we’ve reached mid-October, this is no longer an issue here.

Winter rye cover crop headed up in early May.
Photo Pam Dawling

Winter-hardy grass cover crops to sow in October

Winter rye and winter wheat can be sown in the mid-Atlantic in October. Wheat has less of an allelopathic effect on small seeds, the inhibition of germination that lasts three weeks after rye is turned under. Wheat doesn’t produce as much biomass as rye, so there’s the tradeoff. We sow wheat if the area is ready for cover crops 20-40 days before frost, allowing us to make faster use of those plots in the spring, compared to plots sown to rye.

Winter wheat prevents erosion, suppresses weeds, scavenges excess nutrients, adds organic matter, encourages helpful soil microorganisms, and the fine root system improves the tilth. It is less likely than barley or rye to become a weed; easier to kill than barley or rye; cheaper than rye; easier to manage in spring than rye (less bulk, slower to go to seed); tolerates poorly drained, heavier soils better than barley or oats.

The challenges of wheat are that it does not have good tolerance of flooding, and is a little more susceptible than rye or oats to insects and disease.

For us wheat is a good, trouble-free winter cover crop. The later it gets towards our cover crop cutoff date of November 15, the more likely we are to choose rye. Also, of course, if we have already used all our wheat seed! Winter rye is hardier than any other cover crop and can take later planting dates. More about Last Chance Cover Crop next month. Then I will also write about how to protect the soil over the winter if it is bare.

Austrian Winter Peas graphic

 

 

Secondary cover crops in October: Include legumes where possible

See my September post for more about the benefits of including legumes with winter cover crops grasses. Also how to inoculate legume seeds with the nitrogen-fixing bacteria. See Working with the time you have left for options if you are in another climate zone.

Another key to success with fall sown legumes is to sow early enough to establish before winter halts growth, and to plan not to need that plot next year until flowering time for that legume. 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, and won’t be able to supply all the N needs of the following food crop. Crimson clover flowers in central Virginia 4/16-5/2, most usually around 4/20. Austrian winter peas bloom at the end of April, and hairy vetch in early May.

October 15 (our average frost date) is our clover/peas watershed (legume-shed?). Before that date we use crimson clover; after it (until 11/8, 3 weeks after our average frost date) we sow Austrian Winter Peas, along with winter rye or winter wheat.

Austrian Winter Peas. Photo UAEX Edufarm Ranch Resource Library

More about Austrian winter peas

Austrian winter peas can be sown later than other legumes.

  • Hardy type of Field Pea. (Black peas)
  • Winter-kill in zone 6, hardy in zone 7. Hardy to 0°F (-18°C). (Canadian/spring field peas are hardy to 10-20°F (-12° to -7°C))
  • Can sow several weeks later than clovers
  • Sow at least 35 days before first hard freeze (25°F/-4°C). In zone 7a, 8/10–11/8
  • Optimum temperature for germination is 75°F (24°C), minimum germination temperature 41°F (5°C)
  • Good at emerging through crusted soil
  • Tolerate a wide range of soil types
  • Make rapid spring growth in cool weather
  • Suppress weeds, prevent erosion
  • High N-fixers – a good stand can provide enough N for the following food crop when incorporated
  • They fix as much, or more, nitrogen than crimson clover
  • More dry matter than hairy vetch (which produces more than crimson clover) in the SE
  • Can be mixed with grasses for vertical support, more biomass and better weed suppression
  • Suppresses Septoria leaf spot in tomato crops the next year
  • Blooms late April at Twin Oaks, before hairy vetch
  • Flowers attract beneficial insects (especially honeybees) and reduce aphids
  • The tendrils and shoot tips make a nice addition to salads or stir-fries in early spring
Winter rye with Austrian Winter Peas. Photo Cindy Conner

Cautions with Austrian winter peas

  • Pea seed cannot be stored long. The germination rate could be only 50% after 2 years. Run a germination test if you have seed you are unsure about.
  • Seeds are large and heavy – high sowing rates (compared to clovers). Cost/area is fairly high, a little higher than vetches
  • If you haven’t grown peas or beans on that plot for some years, inoculate the seed.
  • Winter-killed in zone 6, at 0°F (-18°C). For the best chance of winter survival in cold areas, choose your sowing date to get plants 6-8″ (15-20 cm) tall before the soil freezes. (Hairy vetch is more cold-tolerant than AWP.)
  • Sowing in a mix with a winter grain will improve cold weather survival by reducing soil freezing and heaving.
  • May not do well if sown in spring – require a cold dormant spell.
  • Not tolerant of flooding, drought, high traffic, salinity, heavy shade, long cold spring weather below 18°F (-8°C) with no snow cover, or hot (or even warm) weather.
  • Do not regrow after mowing or grazing once blooming starts.
  • Peas on their own do not add much organic matter to the soil – the vines break down quickly.
  • May increase 39 species of pest nematodes, so if you are already having trouble with those, this is not a good cover crop for you.
  • Susceptible to Sclerotinia crown rot, which can completely destroy crops during winter in the mid-Atlantic. One reason not to grow pea crops on the same land two years running.
  • Can also be host to Sclerotinia minor, Fusarium root rot and Ascochyta
Cover of Managing Cover Crops Profitably book from SARE

More resources on Cover Crops

My book Sustainable Market Farming has a chapter on cover crops and many pages of charts about particular options.

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book for $19 or download it as a free PDF from SARE.

Book Review The Ecological Farm by Helen Atthowe

Front cover of The Ecological Farm

 The Ecological Farm: A Minimalist No-Till, No-Spray, Selective Weeding, Grow-Your-Own-Fertilizer System of Organic Agriculture, Helen Atthowe, Chelsea Green Publishing, 2023. 368 pages, $44.95.

 In this inspiring book, Helen Atthowe explains her 35 years of experience farming fruit and vegetables in Montana, California and Oregon. This book will appeal to all those (especially orchardists) who are fine-tuning their land management. I think beginners could find it over-whelming, unless they take it in rich small doses! This is definitely a book to dip into and come back to as needed. It provides a Big Picture of ecological farming, not a step-by-step How To.

Helen clearly pays exquisite attention to her farming, conducts research and share her knowledge with others. She operated an Organic orchard in California, together with her husband Carl Rosato, who very sadly died in a farm accident in 2019. Helen and Carl together pioneered ways to raise tree fruit with no pesticides at all. Helen has expertise in ecological weed, disease and pest management, minimal soil disturbance, and managing living mulches, providing soil fertility without manure-based compost, and cultivating habitat for beneficial species. There is lots to learn from this book.

The endorsements for The Ecological Farm are staggering: fifteen well-known ecological farmers (fourteen men and one woman, what’s with that?). Clearly, this work is held in high regard by many experts in the field. The love of farming goes beyond achieving high crop yields, embracing connection with the land and all its forms of life. Helen says “The process of creating farms and gardens opens my eyes to awe, attunes my ears to listening, and offers the gifts of curiosity, discovery and deep connection.”

The ecological approach in this book goes beyond organic, which in the wrong hands simply substitutes a different set of substances for the banned ones, and doesn’t look any deeper. Helen has measured the effects that her actions have had on her land and crops, and shares her results so that we too can grow nutrient-dense foods and leave the environment in a richer, more balanced state than we found it.

The book contains dozens of Helen’s own beautiful full-color photos of plants, pests, birds, fruit trees and vegetables in various combinations. There are prepared forms for monitoring problems and planning interventions. There is a Vegetable Crop Growing and Troubleshooting Guide, a section on Vegetable Crop Insect Pests and Interventions, one on vegetable crop diseases, and similar sections for tree fruit crops.

The first half of the book sets out ten empirical and practical Principles for Managing Ecological Relationships. As the name emphasizes, it’s about managing relationships, not managing crops for highest yields, regardless of what else happens. The connections that form healthy farming ecosystems require us to pay attention, and avoid outside inputs in favor of balancing what is happening on our own farm. There are some excellent charts of applying the ecological principles.

The Principles include creating above- and below-ground diversity; minimizing soil disturbance; maintaining growing roots year-round (living plants secrete 30-60% of the carbon they capture from the air during photosynthesis down into the soil); growing your own carbon; adding organic residues all season; focusing on carbon fertilizers; recycling rather than importing nutrients; fertilizing selectively; weeding selectively; and creating beneficial habitat as close to the crops as possible.

There are many ways to build soil organic matter without removing large quantities of inputs from someone else’s land (not sustainable or fair, as Helen remarks); many ways to build habitat for beneficial organisms; many actions that can steer plants, animals and fungi towards better balance, so that the soil microbial community will thrive and cycle nutrients continuously.

Helen tells that when she started farming, she behaved like a “nitrogen hoarder”, focused on maximizing the amount of nitrogen the soil had available, and topping it up with compost and cover crops if the soil held less than the requirement for the next crop. Her soil management went through a three-stage evolution: She started to view the abundance and diversity of active microbes as the important bit, and the nitrogen level as merely a sign of that activity. Next, she moved to consider the whole soil organic matter system, rather than the parts as separate features to measure. Thirdly, she researched soil carbon and realized that microbially-active carbon was essential fuel for the soil microbes, and deserved more attention.

Actual measurements showed that, contrary to careful calculations, her soil levels of nitrogen, phosphorus and potassium were becoming too high. Helen had been generously adding sheep manure and clover compost at 7-10 tons/acre (18-25 tons/ha). She changed to using mown clover as her main fertilizer, and learned to manage the carbon:nitrogen ratio, with the goal of achieving steady decomposition of organic residues and increased microbe populations and diversity. Simply adding more high-nitrogen material will not provide good crops! We need to build carbon in our soils, and optimize organic matter decomposition and nutrient cycling.

Helen discovered that the C:N ratio of mowed clover living mulch residue varied according to the time of year, being highest (least nitrogen, nodules not yet formed) in July and lowest (most nitrogen, clover flowering) in August and September. This affects nutrient availability and decomposition rate. Vegetable crops do best in Helen’s system if she tills once a year and regularly applies both high-C and low-C residues on the surface. The continuous organic surface residue supply is much better than an annual large dose. Timing when and how we apply organic residues influences their C:N ratio, and hence how we build up carbon in the soil.

Minimizing tillage is another way to build soil organic matter. Incorporated clover releases nitrate-nitrogen into the soil much more quickly than surface-applied cut clover. If your soil has an active and diverse microbial community, incorporating legume cover crops in spring can give a quick burst of nitrogen (for a few weeks), then a sustained regular release of more as it slowly decomposes. With no tillage there is a lag time. No-till does keep the fungal food webs unbroken, which has advantages. It is important to focus on the carbon fertilizers rather than fast-release nitrogen fertilizers. Since 2016, Helen has used only mowed living mulch as fertilizer for most crops, paying close attention to the timing of mowing. The vegetable plots also benefitted from the living mulch in the row middles growing over the bed after the food crop was finished.

I had to look up “row middles” to understand the methods better. With rows of fruit trees, row middles are the aisles between rows of trees. They can be planted in cover crops, which can be mowed and the cut material blown into the tree rows to act as mulch. The photos of vegetable production (other than her home garden) seem to show aisles wider than the beds, so that less than half of the land is in vegetables and more than half is in cover crops. This fits with the method of growing lots of cover crops as the main source of soil fertility. And with Helen’s method of always leaving half of the living mulch row middles unmowed to provide good habitat for beneficial insects. Over here on the East Coast, I am more used to intensive vegetable farms with narrow aisles between beds, perhaps because land is more expensive, perhaps because Bermuda grass is so invasive as to scare off anyone who might consider permanent paths. Jennie Love, a flower farmer in Philadelphia, uses Living Walkways. Hers are 21″ wide, mostly grass and weeds, and require mowing every single week. Helen’s are more focused on legumes, especially clovers.

To focus on a soil organic matter system driven by microbial activity, attention goes to C:N ratios, optimal decomposition speed and nutrient cycling of the cover crops, mulches and composts. As Helen admits, this can be overwhelming, so don’t change everything at once! As you gain experience growing your own fertilizers, you can cut back on imported fertilizers. Do provide a diversity of organic materials throughout the growing season. Having just one kind, all at once is, for the soil, like us eating a whole giant cheese pizza! Soil “indigestion” takes the form of an over-population of just a limited specific microbial community.

Decreasing nutrient inputs and increasing application of organic residues leads to an increase of mycorrhizal fungi. Including chipped woody compost increases the soil carbon. Adding cover crops increases not just the soil nitrogen but also the carbon as more microbial bodies are born, feed and die. Raw organic matter is to be avoided as it acts like an unmanageable surge that can burn plants (by releasing high levels of salts and toxic byproducts) and leach nutrients. In hot humid climates, it is best to aim for slow decomposition to balance the climate’s effect causing fast decomposition. Aim for ten weeks’ worth of nutrients, not more, and watch for foliar signals of nitrogen or phosphorus deficiency that last for more than 3 weeks – a sign that things are out of balance.

In early spring (if early harvest is a priority) you will need to provide easily available nutrients. The first couple of years after switching your focus to carbon, you may be frustrated by the slow rate of decomposition and the lower yields. It takes weeks longer for surface-applied plant matter to release its nutrients than it does for tilled-in plant matter. This requires patience, planning and also has financial implications. Wait 2-4 weeks after incorporating organic residues, or 4-6 weeks after spreading them on the surface, before planting. Animal manure is not essential for soil fertility. After all, animal manure is simply plant matter that has been partially digested. By applying the plant materials to the soil surface, the digestion is done by small soil animals. It’s not so different!

Letting living mulch grow tall in very wet or very hot weather will help dry or cool the soil, but don’t let the cover crop out-compete the food crops for water! Adding cut covers is also a way of adding to soil moisture. Helen is a fan of minimizing tillage, not of banning it.  Tillage decreases organic matter, microbial diversity and abundance, and disrupts the fungal chains. Strip tillage tills out narrow strips to plant into, from an existing sward of cover crops. Tillage incorporates organic residues, adds air, and stirs up a burst of biological activity, helps warm up spring soils, reduces weeds and breaks up compaction. These benefits can be put to use rather than scorned. “Practice tillage with intention” as Helen advises.

Likewise, compost can be useful when starting on poor land, or needing to address some other kind of imbalance. Don’t rule it out completely! There is plenty of information about making good compost here. Did you know the critical temperature for killing most weed seeds is 145˚F (63˚C)? This book also offers a recipe for a liquid fertilizer for “emergency use” on crops showing a nutrient deficiency.

Author Helen Atthowe.
Credit Cindy Haugen

I appreciate reading work by growers such as Helen, who have done the research and experimentation and responded to the science. An average of one page of footnotes per chapter backs up her claims. I’m not a fan of myths and “woo-woo” gardening. This book includes many useful charts and graphs, so you can see the facts. A four-year experiment started with a 50-year old grass, clover, alfalfa and weed pasture, was divided into two fertility treatments. The first was strip-tilled, with the mowed living mulch blown onto the 4′ (1.2 m) wide crop plots each spring. The second was similar, with the addition of 4″ (10 cm) of clover/grass/weed hay mulch in the late summer before the spring strip-tilling. The hay was cut from another field on the farm. Crop yields were economically sustainable in both plots all four years, and there were almost no insect or disease problems. Yields improved in the second and third years. Yields of some crops were higher with the hay addition – peppers and onions significantly; dry beans and cabbage slightly.

The information on choosing cover crops advises using mixes of crops with different C:N ratios, and including legumes whenever possible. This chapter includes recommendations on inoculants, cover crops for various soil types, and “biographies” of four perennials, 15 annuals and the biennial yellow sweet clover.

The book reminds (or informs) us that being able to stop using pest control sprays starts with building the soil, making it comfortable for soil microbes and creating habitat for natural enemies of the pests. The next step is growing healthy plants, by providing optimal conditions of light, temperature and water, and managing plant competition from weeds or over-thick sowing. After that, focus on the balance of nutrients in the soil, especially carbon.

Suppress pests, rather than focusing on killing them. Spraying insecticides, even organic ones, can disrupt balance and leave you inheriting the task of the creatures you killed. Killing all the prey starves the predators who were keeping the prey in check. Learn to intervene with the least possible impact. Tolerate non-threatening amounts of pest damage. Approach in this order: prevention, pest diagnosis, research, monitoring and ecological decision-making. Minimal-impact interventions include trapping and pest-specific microbial insecticides like Bt (which could require ten sprayings to achieve 98% damage-free Brussels sprouts); moderate-impact interventions include broader-spectrum microbials and materials like soap, horticultural oils and minerals; heaviest-impact interventions (those likely to injure non-targets) include using neem oil, pyrethrin, pyrethrum powder and spinosad.

Designing and maintaining a disease-suppressive ecosystem is the title of the section that focuses on preventing diseases. Crop rotations and diversity of crops and other plants are at the top of the list.

Plant competition is the description of the effect of weeds and over-thick planting. We are encouraged to focus on the weeds most likely to cause problems leaving those that can peacefully co-exist with the crop. Knowing and understanding weed ecology is important: when and where does this weed do best? How can you make your vegetable gardens less comfortable for the weed?

Perennial weeds that spread underground need good attention. Helen deals with quack grass, which takes about four years to become a serious invasion problem, when three passes with the tiller 7-10 days apart in spring are needed. I’ve lived with quack grass (couch grass), a cool-weather invasive. It’s a challenge, but I do think the warm-weather Bermuda grass (wire grass) is worse. Tilling also deals with that.

Crop rotations, especially of crops that grow in different seasons, underground crops that need soil disturbance to harvest them, and crops that rapidly cover the soil, are a big help. Helen recommends growing a full-season perennial cover crop on 25-50% of your garden beds or farm area in production each year to break annual weed cycles.

Some cover crops, including cereal rye, hairy vetch, red clover, sunflowers and mustards all exude allellopathic compounds that inhibit germination of nearby seeds (weeds and crops). Often incorporating the cover crop in the soil works better than chop-and-drop, as buried plants decompose without much air, giving a stronger effect. Also tilling reduces the immediate competition from weeds. Tillage can increase yields even if you believe no-till is best! It’s a trade-off. Tillage reduces soil health. Perhaps the sweet spot is minimal tillage, such as strip tillage. Landscape fabric (reused for ten years) offers another method of weed management.

Part Two of the book (approximately half of the pages) covers an ecological approach to crop management and troubleshooting. I didn’t take as many notes of that. After the introduction to some techniques like interplanting, succession planting, making your own microbially-amended seed growing mix, and using season extension tools, the book focuses on thirty popular crops, with tips on crop management, pests and problems.

A tidbit I learned with spinach is that fall-sown plants that reach the two-true-leaf stage before winter will resume growth in late winter. I also learned that the western striped cucumber beetle has a reddish thorax, making it look more like our striped pigweed flea beetle without such sturdy leg muscles.

The crop management sections include soil and fertility needs and special ecological preferences. The problems sections describe symptoms first, then causes, then resistant cultivars and other strategies for avoiding that problem in future. A valuable reference, and good winter browsing when reviewing the season past and preparing for the coming year. The index covers a substantial 18 pages, in three columns, promising to be comprehensive!

Helen Atthowe still acts as advisor to her previous farm, Woodleaf Farm in eastern Oregon, and is a farm consultant in the US and internationally. I notice that Helen is a speaker at the November 2023 Carolina Farm Stewardships Sustainable Farming Conference.

Helen Atthowe, November 2017.
Photo from Veganic World

Planting winter hoophouse crops

Our first hoophouse radishes germinated three days after sowing. We sowed Cherry Belle and White Icicle. We would have sowed Easter Egg if we’d had enough seed left after the outdoor fall sowings.
Photo Pam Dawling

We’ve already prepared our first bed in the hoophouse and sowed our first few crops (spinach, radishes, scallions, tatsoi, Bulls Blood beets and cress). We spread the bed prep out over 5 days and the sowings over 2 days. I’ve written lots about our fall hoophouse planting, so I’ll give you links, mention a few updates and stick to photos otherwise.

Mid-October photo of September-sown tatsoi and August-sown Tokyo bekana. Fast-growing crops make good use of small windows of time.
Photo Pam Dawling
  • Hoophouse Winter Schedule Tweaks and Improvements (pack more crops in, get higher yields, reduce or spread the workload). One change we made was to sow some early catch crops in areas that weren’t needed for all-winter crops until later. We mostly used tatsoi and Tokyo bekana, both fast–growing leafy greens. We intended to grow some early beets too, but the seed didn’t germinate. A new crop last winter was cress, Creasy Greens Upland Cress and Belle Isle Upland Cress from Southern Exposure. They take 50 days to maturity (in spring). We had two good intentions we did not manage to follow through on. One was to let some of the cress flower, to feed beneficial insects. And I think we got too impatient. The other was to notice which one of the two kinds we prefer and just grow that one. We didn’t manage to keep good enough records on that, so this winter we are obliged to repeat the experiment, with more good intentions!
Belle Isle Upland Cress from Southern Exposure Seed Exchange
  • Using all the space in the winter hoophouse (filler crops for random spaces, fast-growing catch crops, radish sowing dates for seamless harvests.)
  • Fall hoophouse bed prep and shadecloth removal (packing away the giant piece of shadecloth until May, spreading compost, broadforking and raking the beds, direct sowing the first bed, sowing seeds in an outdoor nursery bed to transplant into the hoophouse a few weeks later). This post includes a step-by-step guide to hoophouse fall bed prep. Our soil is improving each year, becoming easier to broadfork and rake. That counters the aging process of our human bodies! One change we made last year was to measure and pin down the drip tapes 12” (30 cm) apart, and use the drip tape as a guide to making furrows (drills). This is easier than using the row marker rake, as we used to do.

    Our hoophouse with shadecloth for growing summer crops. Photo Pam Dawling. We have now sewed the two pieces together, to avoid the gaping hot spot in the middle!
  • Hoophouse fall bed prep (includes an appreciation of spiders and a video of spider “ballooning”)
  • Sowing hoophouse winter crops (more details on bed prep tools and techniques, including the row marker rake if you want to use that, and links to posts about winter lettuce varieties we used in 2017/2018.)
  • Planning and Growing Winter Hoophouse Vegetables (hoophouse crop map, many links to other posts including a video and three slideshows, crop rotations, choosing winter hoophouse crops, posts about specific crops (with all the details), back up plans in case something goes wrong, and harvesting.)

    Mid-October emergency back-up seedlings for the hoophouse.
    Photo Pam Dawling. We needed to compensate for poor germination that year.
  • Preparing your hoophouse for fall and winter (includes one of my slideshows, and a more detailed discussion of lettuce types and sowing dates, information about salt build-up and our wash-down strategy in a 3-slide mini slide show, when we close and open the doors and windows, and a Be-Prepared Winter Kit list)
  • Planning winter hoophouse crops – our step-by-step process for hoophouse crop planning.

    Spinach seedlings (from pre-sprouted seed) emerged on the third day after sowing. here they are on day 4. Photo Pam Dawling
  • Winter hoophouse growing (includes a round-up of earlier posts, and a discussion about the value of crop rotation in the hoophouse, and a list of 20 benefits of having a hoophouse.)
  • Spinach variety trial conclusions This year we are growing Acadia.  Johnny’s do not recommend this variety for late fall or winter sowing, but it did very well in our hoophouse, sown in September, October, November and January.
  • September in the hoophouse: sowing spinach 
Two jars of sprouted spinach seeds and grits to prevent the damp seeds clumping. presprouting spinach seeds for a week in a fridge gets round the impossibility of getting spinach to germinate in hoophouse soil at 80F (27C) as it is September 11.
Photo Pam Dawling
One side of our hoophouse on Sept 10. Three beds with cover crops of buckwheat and sunnhemp (which got bitten down at a young age by Something), and one bed under solarizing plastic in hopes of killing nematodes. Photo Pam Dawling
Zipper spider on the pepper plants in our hoophouse September 10.
Photo Pam Dawling

Cover Crops for September: wheat and crimson clover

Crimson clover is a beautiful and useful cover crop.
Photo Kathryn Simmons

Note: the day after I posted this I found I was mistaken in believing barley to die at a warmer temperature than oats, so I’ve edited it.

Focus Cover Crops for September: Winter Wheat and Crimson Clover

In August I wrote about cover crops such as millets, southern peas, buckwheat which are frost-killed. If it’s still too early to sow your winter cover crops, sow summer cover crops. Before I get to the wheat and crimson clover, I’ll mention some other useful seasonal cover crops.

Winter-killed, not frost-killed, cover crops

There are also cover crops that are not frost-killed, but die later in the winter, at colder temperatures, such as oats and barley. Only sow oats or barley if you are sure you can get them turned under or killed by cold winter weather before they seed. They will not mow-kill, so if the weather doesn’t kill them, you will have to turn them under. Be careful buying feed-grade seeds (rather than Organic seed-grade), as they can contain weed seeds including GMO canola.

Late corn undersown with oats, now mowed high, and the sweet potato patch now sown in winter wheat and crimson clover.
Credit Ezra Freeman

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 14-20, the cut-off date for oats is September 7, or September 15 if we really push it. Sowing too late means you don’t get enough growth in the fall, and the soil is not adequately protected from erosion or from weed growth.

We sow oats after growing early sweet corn, spring broccoli, spring-planted potatoes, cabbage, kale, or early season spinach, lettuce, beets, carrots. Spring oats die after three nights at 20°F (-7°C), or a single plummet to 6°F (-17°C), leaving the plot quick to prepare for early crops next year. Winter oats are hardier, but my goal with growing oats is for them to die in winter. 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.

Don’t let your cover crop barley go to seed! Photo USDA

Fall-sown barley (Hordeum vulgare), grows even faster than oats, but not as quickly as winter rye, and it won’t die as early in the winter as oats. Barley dies at 17°F (-8°C). It usually will die in Zone 7 and colder regions. The dead barley residue protects the soil through the winter, and dries into what Barbara Pleasant calls “a plant-through mulch” in spring in cold zones.

See Planning Winter Cover Crops, a post that includes my Short Simple Guide to Winter Cover Crops and my slideshow Cover Crops for Vegetable Growers. Oats, barley, wheat and rye sown too early can head up and seed before you get to winter, making them less useful, and more of a weed problem.

Winter-hardy grass cover crops to sow in September

It is too late for us to usefully sow cover crops that are not frost-hardy, as they won’t make enough growth before getting killed.

Winter rye and winter wheat are two grass cover crops that can be sown in the mid-Atlantic in September. Wheat is easier to incorporate than rye and has less of an allelopathic effect on small seeds, the inhibition of germination that lasts three weeks after rye is turned under. It’s true wheat doesn’t produce as much biomass as rye, so there’s the tradeoff. We sow wheat if the area is ready for cover crops 20-40 days before frost. This allows us to make faster use of those plots in the spring, compared to plots sown to rye.

Winter wheat
Photo USDA

For us wheat is a good, trouble-free winter cover crop. Winter wheat prevents erosion, suppresses weeds, scavenges excess nutrients, adds organic matter, encourages helpful soil microorganisms, and the fine root system improves the tilth. It is less likely than barley or rye to become a weed; easier to kill than barley or rye; cheaper than rye; easier to manage in spring than rye (less bulk, slower to go to seed); tolerates poorly drained, heavier soils better than barley or oats. If you have leftover seed, wheat can be sown in spring – it will not head up, but “wimps out” when the weather gets hot.

The challenges of wheat are that it does not have good tolerance of flooding, and is a little more susceptible than rye or oats to insects and disease.

Secondary cover crops in September:  Include legumes where possible

With careful planning, you can grow next year’s fertilizer for your later spring-planted vegetables! Legumes grow nitrogen-fixing bacteria on their roots, which can feed the next food crop. You may need to buy a suitable inoculant if you are introducing a new legume species. You may decide to inoculate anyway, for insurance, even if that type of legume is already somewhere in your garden. Before sowing the legume seed, dampen it, sprinkle the inoculant over the seed at a “pepper on your dinner” rate, and stir it in. Then sow the seed. Be sure not to make the seed wetter than slightly damp, or you’ll need to spread it out to dry a bit before you sow.

Two other key parts of being successful are to sow the legume early enough to establish before winter halts growth, and to plan not to need that plot next year until flowering time for that legume. At flowering time, legumes have the maximum amount of the nitrogen nodules they will have. Don’t let the legume flowers set seed, or they may become a weed problem. Take notes on when various legumes flower. 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, and won’t be able to supply all the N needs of the following food crop.

September (40-60 days before frost) is a good time to sow clovers here, provided you can supply enough overhead irrigation. They will make some growth in our climate before winter, and then a lot more once spring arrives.

Crimson clover cover crop with bumblebees.
Photo Bridget Aleshire

Crimson clover is a good September choice, if you won’t need to prepare the area before it flowers (in central Virginia 4/16-5/2, most usually around 4/20).

For a cover crop to survive the winter, sow winter wheat with Austrian winter peas, crimson clover, hairy vetch, red clover, white clover or 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.

Clover for green fallow in early September

See August’s post for info on planting a Green fallow plot (Full year cover crops)

Time is running out on this for us, but you may still have enough warm weather where you are. A green fallow crop (all-year cover crop) will replenish the soil and reduce annual weeds for the following year. In late August, or early September, four weeks after transplanting your fall brassicas, especially cabbage and broccoli, but also kale and collards, broadcast a mix of clovers: 1 oz (30 g) Crimson clover, 1 oz (30 g) Ladino white clover and 2 oz (60 g) Medium red clover per 100 sq ft (9 m2). Crimson clover is a winter annual and will be the biggest and the first to flower, in April. Medium red clover is a biennial and will be the next to flower. White clover is perennial and will take over the plot as the others subside. Be sure to get the medium red clover, not the Mammoth kind that dies when mowed. Likewise, for maximum benefit, get the tall Ladino white clover, not the low-growing “wild” type. In March, mow down the old brassica stumps and let the clovers flourish. You will be mowing this patch about once a month from March to October next year to prevent the crimson clover and the annual weeds from seeding.

Cover crops to sow soon after your first frost date

I’ll say more about this next month, and because I want this website to be useful to a geographically wide range of growers, I’m including a preview here. If the area is ready for cover crops up to 10 days past the frost date, sow winter wheat or winter rye with 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. Sow winter rye from 14 days before to 28 days after first fall frost. See Working with the time you have left in the Summer Cover Crops post. Austrian winter peas can be sown later than other legumes, it’s too late for clovers.

My book Sustainable Market Farming has a chapter on cover crops and many pages of charts about particular options.

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book for $19 or download it as a free PDF from SARE.

Cover crops for August: Oats and Barley

From the USDA Barley Plant Guide

Note: I edited this post in September when I found I was mistaken in believing barley was less cold-hardy than oats.

Focus Cover Crops for August: Oats, barley and other winter-killed cover crops

In August we are looking ahead, thinking about how our cover crops will be impacted by future cold weather. In July I wrote about hot weather grass cover crops, including Sorghum-Sudan hybrid (Sudex), and the millets, which are not frost-hardy.

German/Foxtail and Japanese millets are day-length sensitive. Growth is considerably less if they are sown after the summer solstice, so they are likely to be of limited use as cover crops once we reach August.

Browntop Millet could be useful in August in the mid-Atlantic. Proso/Broomcorn Millet I’m not so sure about. Pearl/ Cattail Millet is not day-length sensitive. To winter-kill and avoid seed formation, sow 60-85 days before your expected first frost.

See Working with the time you have left in the post Cover Crops in Summer. See No-Till summer cover crops in that same post (Soy, southern peas, foxtail millet). Also there, see Five Easy Summer Cover Crops that Die with the Frost (buckwheat, sorghum-sudan grass, soybeans, southern peas and sunn hemp.)

Buckwheat cover crop in flower.
Photo Pam Dawling

Buckwheat can be sown up to 28 days before the first frost.  See my article about buckwheat. Soybeans can be sown up to 45 days before frost. A mix of sunn hemp, soybeans or southern peas and other frost-tender cover crops can be grown during August (60-80 days before frost) before planting garlic in mid-fall. This method will work more easily if you mow the cover crop around your frost date, so that it is easier to make furrows in the soil. Forage radish, lab-lab beans or bell beans sown now will die back and leave almost bare soil. This is a boon for the very earliest spring transplants or sowings.

Or, instead of sowing a cover crop now, you could sow a fast-growing vegetable crop. Kale, spinach, Tokyo bekana, radishes, chard, lots of salad crops, senposai, mizuna, tatsoi, or land cress. 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″ (30 cm) 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

Winter-killed, not frost-killed, cover crops

In August, we can sow winter cover crops to be winter-killed for easy soil cultivation before early spring vegetables. Oats and barley are in this category. Oats will be killed by three nights of 20°F (-7°C) or a single night of  6°F (-14°C). Sow oats 5-8 weeks before your average first frost to get good size plants before they get winter-killed. We sow in late August and early September in Zone 7a. See Cover Cropping Your Garden by Chris Blanchard in 2002:

“Inexpensive and easy to grow, oats are a standard early fall cover crop in the northern and middle sections of North America.  A quick-growing, non-spreading grass, oats will reliably die in Hardiness Zone 6 and colder, and often in zone 7.”

It used to be nine years out of ten, here in Louisa County, VA, but our climate is shifting to be too warm in winter to reliably kill oats. This past winter (2022/2023) oats did not die. They were cold-damaged, and set back, but definitely not dead.

We can no longer rely on our winter cover crop oats getting winter-killed. March photo by Pam Dawling

Fall-sown Barley (Hordeum vulgare), grows even faster than oats, although not as fast as winter rye, and it won’t die as early in the winter as oats. Barley dies at 17°F (-8°C). It usually will die in Zone 7 and colder regions. The dead barley residue protects the soil through the winter, and dries into what Barbara Pleasant calls “a plant-through mulch” in spring in cold zones.

See Planning Winter Cover Crops. 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.  In central Virginia, it’s a mistake to sow rye as early as August, as it can set seed.

Winter-hardy cover crops to sow in August

Not all winter cover crops can be sown as early as August in the mid-Atlantic. Don’t sow winter rye, or it may head up before winter and drop seeds. Only sow oats or barley if you are sure you can get them turned under or killed by cold winter weather before they seed. They will not mow-kill. Be careful buying feed-grade seeds (rather than seed-grade), as they can contain weed seeds including GMO canola.

Clovers can be sown in August (provided you can supply enough overhead irrigation). September is a better time to sow clovers here, if you are sowing them in bare ground. They will make some growth in our climate before winter, and then a lot more once spring arrives.

Secondary Cover Crops in August: Undersowing for more cover crops

  • Choose vigorous food crops, but cover crops that are only moderately vigorous.
  • 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. Often the best time is at the last cultivation.
  • The leaf canopy of the food crop should not yet be closed. With vining food crops, sow the cover crop before the vines run.
  • Ensure a good seedbed and a high seeding rate.
  • Irrigate sufficiently. The food crop will have good roots by then, but the cover crop seed will be just below the surface and will need some help to germinate.

 Green fallow (Full year cover crops)

Fall broccoli undersown with a mixed clover winter cover crop.
Photo Nina Gentle.
  • Our main use of clovers is to undersow fall brassicas such as broccoli and cabbage, with a mix of Crimson clover, white clover and medium red clover in August, to form a green fallow crop (all-year cover crop) for the following year, replenishing the soil and reducing annual weeds.
  • 2 weeks after transplanting the brassicas (August), we hoe and till between the rows, or wheelhoe.
  • We repeat at 4 weeks after transplanting, and broadcast a mix of clovers (late August-early September): 1 oz (30 g) Crimson clover, 1 oz (30 g) Ladino white clover and 2 oz (60 g) Medium red clover per 100 sq ft (9 m2)
  • In March, we bush hog the old brassica stumps and let the clovers flourish, mowing once a month to prevent the crimson clover and the annual weeds from seeding.

See my Mother Earth News post: Late summer and fall intercropping of cover crops in vegetable crops, aka undersowing.

If you have difficulty getting even coverage when broadcasting clovers or other cover crop seeds, try seeding half the crop walking in one direction, and then seed perpendicularly across your original path

In mid-August, we undersow our last sweet corn planting with oats and soybeans, as the winter cover crop, which winter-kills, leaving a plot that is easily worked up next spring. Our 6th sweet corn is sown 7/16. 4 weeks after seeding, we cultivate and sow oats and soy. In mid-March we follow with our spring potatoes. Both oats and soybeans have some tolerance for shade and for foot traffic (harvesting corn!).

Late season sweet corn undersown with oats and soy
Photo Kathryn Simmons

Sweet corn can be undersown with clover rather than soy or oats in some climates. We tried clover but found it harder to germinate in hot weather, and harder to keep the tiny seed damp. Buckwheat can be undersown in corn as a short term summer cover, but according to Sue Ellen Johnson, (co-editor of Crop Rotation On Organic Farms: a planning manual, it grows rather straggly in the shade of the corn. Soy has the advantages of tolerating shade as well as foot traffic.

We tried an idea from NY State, or undersowing winter squash with buckwheat and tilling it under just before the vines run (that was June), but here in the south, the vines ran too fast. We ended up having to wade in among the vines to pull up the buckwheat by hand!

You can drill cover crop seeds using a push seeder. See VABF Using Manually-Operated Seeders for Precision Cover Crop Plantings on the Small Farm. Don’t worry if the seed ends up deeper than ideal. It will still germinate. On a small scale, you can sow by hand, either broadcasting and raking in, or in close rows using a hoe, as if sowing

Cover Crop Planning

My book Sustainable Market Farming has a chapter on cover crops and 9 pages of charts about particular options.

The book Managing Cover Crops Profitably (third edition) from the Sustainable Agriculture Research & Education Program (SARE), is the best book I know on the subject. You buy the book for $19 or download it as a free PDF from SARE.