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.

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.