Winter Cover Crops for Your Vegetable Garden

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Hairy vetch makes an excellent cover crop for overwintering

Yesterday as I pulled up weary tomato plants and lugged them to the compost pile, I considered my options for the empty bed. I could cover it with a winter mulch, but with a few weeks of growing season left to go, cold-hardy cover crops are a better option. From nitrogen-fixing legumes like hairy vetch and winter field peas to deeply-rooted winter grains like cereal wheat and grazing rye, winter-hardy cover crops improve the soil and green up first thing in spring - an awesome sight to a winter-weary gardener.

Experiments with Winter Legumes

Legumes including peas, beans and vetches can take nitrogen from the air and store it in their roots, so you can use cold-hardy legumes to grow your own fertilizer during the winter and early spring months. One of my favourite winter cover crops is hairy vetch (Vicia villosa). When grown before tomatoes, hairy vetch can enhance their productivity and boost tomatoes' ability to resist common diseases. Hairy vetch is also a choice cover crop to grow in areas to be planted with sweet corn, peppers or other summer crops. Planted in early fall, hairy vetch plants stay small through winter, surviving winter temperatures of -20°F (-29°C). The plants quickly grow into a thick tangle of foliage in spring. When cut off at the soil line, the foliage dries into a mulch that can be rolled up like a rug. Below ground, nitrogen nodules on rotting hairy vetch roots provide a steady supply of nutrients for the cultivated crop.

Crimson clover
Crimson clover, the most beautiful of green manures

In areas where winter temperatures are not likely to drop below 0°F (-18°C), you can grow crimson clover, the most beautiful of all winter legumes. Crimson clover is an ideal cover crop for soil that won't be needed until early summer, though you have the option of turning under the plants as a green manure whenever you like. I think crimson clover's beautiful red tops are worth waiting for, and you can double your pleasure by adding blue cornflowers to the planting.

Other hardy legumes including winter field beans and winter field peas can survive winter temperatures of 10°F (-12°C), but they are such gangly plants that they are best grown in combination with upright cold-hardy grains like cereal wheat or grazing rye. In spring, when the plants are about knee-high, the entire mass can be pulled and composted, or mowed down and turned under. In Winter Grains for your Garden, I explain how to work with cereal wheat and rye by planting whole "berries" purchased at health food stores.

Winter wheat cover crop
Winter wheat makes a good grain for use as a overwintering cover crop

Using Cover Crops to Improve Drainage

In the US, quite a bit of research has gone into using daikon radish as a fall cover crop. The huge roots can penetrate compacted subsoil, and when the plants die from cold temperatures, the rotting radishes improve the soil. Indeed, any plants that grow into a lush sea of green in the fall and then die in the winter will leave behind deep pockets of organic matter. In this way, fast-growing mustard and turnips can be used as winter cover crops should you have seed to spare.

Like most gardeners, I have a fair share of dandelions in my garden, but I ignore the little seedlings I see in the autumn. When I wait until early spring to pull them out, they usually come up with a thin taproot more than a foot (30 cm) long. Humankind has yet to invent a tool that can create deep aeration holes in the soil as easily as I can pull up dandelions after a drenching spring rain. I would never plant dandelions on purpose, but they have their place among winter cover crop plants for vegetable gardens.

By Barbara Pleasant

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Comments

 
"My garden got flooded and damaged from the recent Hurricane that happened while I was out of state. I couldn't harvest or prepare anything, so some things bent back my wire fencing and things trampled over my garden, damaging my raised beds and tore out plants. How do I safely clean this up for next spring. I considered fall planting, but at this time in Virginia, I am not sure I want to kill myself trying to beat the fall planting deadline. So I want to concentrate on making my garden healthy. Several questions - 1. Should I re-till the whole plot (20'x40), add in compost and natural fertilizers, and plant ground cover and let it set for the winter until March/April when I can plant again? or 2. Should I dig up and haul away the nasty flooded over dirt? Start from scratch again? Any answers, comments, feedback, knowledge would be appreciated. "
Charlotte Ross on Friday 16 September 2011
"Where can you find hairy vetch?"
Carrie on Friday 16 September 2011
"I run a 1/2 acre urban farm. I don't have a lot of fallow land, but was wondering if it would make sense to grow a cover crop between the crop rows? I was planning on planting crimson clover because we have 4 bee hives. Thanks for your thoughts!"
Kay on Friday 16 September 2011
"Charlotte, allow some time for things to dry out, and make plans based on what would be best for your soil over winter -- cover crops are often less labor intensive than mulches...Carrie, my hairy vetch seeds came from Southern Exposure Seed Exchange, but other suppliers have it, too...Kay, some market growers use their pathways to grow a mix of legumes and grasses, then mow it and use the mulch in neighboring rows. Crimson clover might not work as well as dutch white and other clovers, but anything is better than bare soil in the winter."
Barbara Pleasant on Saturday 17 September 2011
"Thank you! "
Charlotte Ross on Saturday 17 September 2011
"I tried to used ipomea batata as cover crop i mean the leaves are fast grower i don't know if this avisable since iwas thinking that instead of grass i'd rather prefer the vegetation of ipomea batata. Please kindly notify me if iwas doing right or wrong"
Jovenal on Sunday 2 October 2011
"What do you find is the best way to kill and incorporate cover crops and green manures in small-scale gardening using hand tools?"
Jennie on Tuesday 4 October 2011
"Jovenal, I think sweet potatoes produce a fine surface mulch, but of course it's gone once the weather turns cold. You could follow sweet potatoes with a winter grain...Jennie, it varies with the cover crop. Annual legumes like hairy vetch and crimson clover die when severed at the crown, and the leaves and stems dry into a surface mulch. I find green manures very difficult to handle unless they are mowed first.Instead of digging in fresh material, I usually pull it up and compost it. The roots left behind rot into soil organic matter."
Barbara Pleasant on Wednesday 5 October 2011
"Barbara may i remind you that in my country there's no winter that's why sweet potatoes is growing well and i find it very advatageous "cause we use the leaves as vegegetables but i wanna know if this advisable as cover plant since it grows vigorously ang i'm afraid this would compete with the growth of the crop i'm planning to sow w/c is tomato."
Jovenal on Wednesday 26 October 2011
"I have a8/20 green huuse and I am growing tomatoes/ squash/ beets/ vinging okra. they are growing good. Iwas just wondering how to and when to transplant these new seedlings this is 2/13 "
ken on Saturday 2 February 2013
"Ken, all except beets are warm-season plants, so they should not go out until after your last frost has passed. This time of year, most people work with cool-season plants like cabbage family crops, lettuce, etc., because they can go out more than a month earlier than warm-season veggies. "
Barbara Pleasant on Saturday 2 February 2013

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