I’m a pretty sloppy vegetable gardener. Someday I’ll get more serious and attentive. But one thing I am serious about and actually do well in the vegetable garden is grow cover crops.
I trace it to being one of the editors 10 years ago of Managing Cover Crops Profitably, a book for farmers published by the USDA Sustainable Agriculture Research and Education program. I’ve found what works for my area, and would probably work for gardeners across a large swath of the Northeast and North-Central states. But you may want to consult that book or your local Cooperative Extension office for more about what works in your area.
I’ve boiled it down to basically three or four crops:
Summer annual: Buckwheat. I seed this after spring crops such as lettuce, spinach and other greens. Even if you only have a month to devote to a cover in summer, it’s worth growing buckwheat between spring and fall crops. Some other alternatives for this niche are sorghum-sudangrass, millet (cheap birdseed works well in a pinch), soybeans, or cowpeas.
Winter annual: Rye. Winter rye (not to be confused with ryegrass) is the workhorse cover crop in my garden. I seed it from late August until mid-October. It’s cheap. It establishes quickly and easily. Grows late into the fall. Often stays green under the snow and seems to grow if we get a midwinter thaw. Is rock solid hardy. Comes back in spring and puts on a lot of biomass. You need to plan ahead and get out there with a shovel and turn it over well ahead of planting to kill it. I usually use it where I’ll be planting large-seeded crops in late spring or early summer, or transplanting tomatoes or peppers. Other winter grains, such as wheat, work OK. But rye is king.
Winter-killed annual: Annual ryegrass or oats. These are cool-season plants like winter rye. Plant them in late summer or early fall and they grow well in fall. But in our neck of the woods, they won’t survive winter and you’ll end up with a nice dead mulch on top of mellow soil. These are great for places where you’ll plant early in the spring and you don’t want to wait for the soil to dry out enough to turn under an overwintering crop like winter rye.
Where to buy: I’m fortunate that our local Agway (it use to be a big local chain, now it’s more or less a Mom and Pop hardware store/feed and pet supply/garden center kind of place) carries all four of these cover crops. At the appropriate time of the year, they put out a barrel, scoop, bags and a scale. Johnny’s and other seed companies also carry cover crops via their online catalogs.
You can get creative in your purchasing. As I mentioned, I’ve used bird seed in a pinch. There’s all kinds of stuff you can try at your local food coop or health food store (lentils, wheat berries) if you can’t wait for the seed to come through the mail.
Establishment is pretty easy, too. I pull out old plants and weeds. Then I take a stirrup hoe and work the top couple inches of soil. If you have time, wait a week or so to let weed seeds germinate and hoe it again. If you want, you can loosen the soil down deep with a fork before hoeing, but I seldom do. Broadcast the see by hand. I put it on pretty thick — at least a seed every inch. I work the seed in with a heavy rake using a kind of chopping motion. You don’t really want to draw the soil or you’ll end up raking your carefully sown seed to one end of the bed and end up with uneven coverage. The idea it so get the seed incorporated a little, but not too deep.
Then I take the flat part of the rake and pound the soil to firm it up and get good seed-to-soil contact. It sounds counterintuitive to press the soil down when you’re trying to improve it. But trust me, the better germination you get will be worth it. I remember a gardening friend years ago who used a broadcast seeder to do a larger garden patch and had the cover crop come up only where he left footprints.
Here’s what it looks like when you’re done:
I jumped right in here without detailing the benefits of cover crops. Most of you know that they suppress weeds and improve soil by converting all that sunlight that would be wasted on bare ground into organic matter. The fine roots of grasses are especially good at improving soil structure — in my case loosening up clay soil and improving water infiltration.
You may have already noticed that I haven’t mentioned hardly any legumes. Sure, legumes fix nitrogen. But my intuition tells me that in the highly artificial soil in my veggie beds (and probably most other well-tended vegetable gardens), the nitrogen levels in the soil are high enough that legumes don’t fix much nitrogen. (When there’s a lot of free nitrogen, legumes don’t waste much energy fixing more.)
The winter grains and ryegrass are a lot cheaper and more aggressive than most legumes. And they act as trap crops. They are good at catching and retaining nitrogen left in the soil at the end of the growing season and overwintering it in their biomass. Less leaches away, and more is available next season when that biomass breaks down.
So what are your experiences with cover crops?