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 May: Buckwheat

Buckwheat in flower in September.
Photo Pam Dawling

This is the first of a monthly series on cover crops, which will take us through a whole year, to April 2024.

Why Grow Cover Crops?

<a title=”USDA, Public domain, via Wikimedia Commons” href=”https://commons.wikimedia.org/wiki/File:Soil_food_webUSDA.jpg”><img width=”512″ alt=”Soil food webUSDA” src=”https://upload.wikimedia.org/wikipedia/commons/thumb/8/89/Soil_food_webUSDA.jpg/512px-Soil_food_webUSDA.jpg”></a>

See my post Cover Crops in Summer.

  • Cover crops suppress weeds and provide a boost to soil organic matter.
  • Keep live roots in the ground as much of the time as possible, to feed the microorganisms in the Soil Food Web.
  • Here is a diagram of the Soil Food Web: https://upload.wikimedia.org/wikipedia/commons/8/89/Soil_food_webUSDA.jpg
  • Roots anchor the soil, preventing erosion in heavy rains.
  • Dead roots also have a role, providing drainage channels in the soil and letting air in deeper.
  • Adding organic matter to the soil is a way of sequestering carbon, as well as providing nutrients for your crops.
  • Deep-rooted cover crops draw up nutrients, bringing them up where crop plants can access them.
  • Leguminous cover crops provide nitrogen, saving imports of organic fertilizers or a big compost-making operation.
  • Too often, gardeners grow cover crop only in the off-season, to protect the soil in winter, and assume it’s not a summer option. But it is, and planting summer cover crops provides many benefits.

Focus Cover Crop for May: Buckwheat

A bed of young buckwheat with a cosmos plant to attract beneficial insects. Photo Pam Dawling

I have a blog post Buckwheat, a wonderful summer cover crop, introducing an article I wrote for Growing for Market magazine. See that post for basic details I mostly won’t repeat here.

Buckwheat (Fagopyron esculentum) is a fast-growing warm-season broadleaf annual that is a very useful cover crop. Its special strengths are in weed-suppression, attracting beneficial insects, improving the soil tilth (aggregate structure) with its fibrous roots, and extracting potassium, calcium and phosphorus from the soil to the benefit of following crops. Buckwheat is almost three times as good as barley in scavenging phosphorus, and more than ten times better than rye (a poor phosphorus scavenger). Because buckwheat is not related to any of the common food crops, it is simple to include in rotations.

Buckwheat can be sown up from your last frost up to 35 days before first fall frost. Buckwheat can close its canopy in just two weeks, preventing the soil baking in summer conditions. Because it matures quickly, and self-sows, it can be used in several successions with tilling between, to suppress some perennial weeds.

Flowering buckwheat in September.
Photo Pam Dawling

Buckwheat can do fairly well on poor soils, is tolerant of a range of soil pH and is an easy crop to deal with manually or with small-scale equipment. Even mature buckwheat plants are easy to deal with using manual or small-scale equipment. You can just pull up the plants by hand, or use a hoe or scythe to slice them off at the soil line. You can chop them into the soil, or gather them up and compost them. Or you can use a no-till method, let the dead plants die into a surface mulch and plant through them.

Buckwheat yields only a couple of tons per acre, but does it in only six to eight weeks. If you want to increase the (admittedly sparse) biomass, cut down buckwheat just before it reaches 25% bloom, to a height above the lowest leaf node. Buckwheat will regrow rapidly and you may even be able to make a second cutting.

Buckwheat also makes good food for poultry or rabbits, and chickens love the seeds. It does not provide good forage for larger livestock.

Beds of young buckwheat.
Photo Bridget Aleshire

Barbara Pleasant, in her 2009 article Cover Crops, described Rhizodeposition as a special advantage of using cover crops. Many plants release sugars and other substances through their root hairs into the soil. They are solar-powered pumps, sending energy down into the soil, causing the root tips to host colonies of useful microorganisms. As the roots move deeper, the microbes follow. With vigorous winter cover crop plants, like oats or rye, this process goes on down to 6 feet (much more deeply than you should dig). Buckwheat doesn’t go very deeply at all, but it can be working for you, which is much better than leaving the soil empty and drying out.

Buckwheat in flower in June. Photo Pam Dawling

Buckwheat Resources

Secondary Cover Crops for May

Soy, mustard, sunn hemp, southern peas are all also good summer cover crops, and I will say more about them in the next few months. See Cover Crops in Summer.

Sunnhemp cover crop at Nourishing Acres Farm, NC.
Photo Pam Dawling

Sunn hemp, a nitrogen-fixing legume from the tropics, can grow as tall as 9’ (2.7 m) in a few months. Sow sunn hemp from a week after your sweet corn sowing date, up to 9 weeks before your first fall frost, which will kill it. It tolerates a wide range of soils (but not if waterlogged). Plant inoculated seed (use the same inoculant as for southern peas) 1” (2.5 cm) deep, with seeds 1.5” (4 cm) apart in the row, and with rows 6” (15 cm) apart. Sowing densely (as with all cover crops) will work better to smother the weeds.

If you sow sunn hemp in a summer gap between spring and fall vegetable crops, it will provide a nitrogen boost for the fall crop, because it is a legume. In dense plantings, it can fix more than 120 lbs (54 kg) of nitrogen and 12 pounds of biomass per 100 sq ft (0.56 kg/sq m). 60 days after sowing, the stems thicken and become fibrous and high in cellulose; cutting at this stage produces long-lasting mulches that increase soil carbon. If you cut the crop back at a younger stage, this will stimulate branching (more biomass) and more root penetration (better drainage).

Sunn hemp cover crop at Nourishing Acres Farm, NC
Photo Pam Dawling

We have taken to sowing sunn hemp as a summer cover crop in our hoophouse, and lopping it periodically with hedge shears to an ergonomic elbow height. This is because we don’t want it to shade crop plants further back (north). The fallen tops make a nice “forest floor” carbonaceous mulch.

Mustard we don’t grow as cover crops, although I do have experience of growing it in England, where it is one of the favorite cover crops for short crop gaps, or in preparing areas reclaimed from pasture or lawn. We have too many harlequin bugs, and we hope to break their lifecycle by having a summer month without any visible brassicas. (We do often have fall brassica seedlings growing under insect netting.) Also, our “crop portfolio” has plenty of brassicas already, and we’d rather have a better rotation, with brassicas less often.

Mustards can decrease weeds, or certain pest nematodes, if you grow the right kind.

Soybeans as a cover crop
Photo agcrops.osu.edu

Soybeans are a great summer cover crop and they are also a legume, so they add nitrogen to the soil. They have good shade tolerance and tolerance to foot traffic (that is, people harvesting crops on either side. Because of this, we like using soy to undersow in sweet corn.

Southern peas are another warm weather cover crop option. They are also a legume, and so will add nitrogen to the soil. Iron and Clay is the sprawl variety best known for cover crop use, but other varieties also work.

Iron and Clay southern peas flowering in September. Photo Pam Dawling

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.

See Harvey Ussery  Four Outstanding Cover Crops for Summer.