A MONTH OR SO BEFORE KILLING FROST, the vegetable-garden soil that fed me gets a meal, or at least the promise of one. I sow soil-sustaining cover crops (always from non-GMO, organic seed) as my various food crops are harvested, gradually turning raised vegetable beds into mini-fields of winter cereal rye (above) and mammoth red clover for the colder months, or maybe a mix of quick-to-grow, easy-to-manage and beautiful field peas and oats.
Come spring, several weeks before I plan to plant each area, I’ll cut or mow or pull the grain and legume combination down, depending on which pair I used and where they’re located, then turn under the remains. It’s like composting in place, with the foliage and underlying root system decomposing to improve soil texture and fertility.
Cover crops can serve other purposes: Some specialized ones, like various Brassicas, can also provide not just biomass but other benefits including pest and disease control (more on that from Cornell). The subject is much wider than this simple explanation, but stated most simply:
- Grasses (like rye, sorghum-sudangrass crosses, and wheat) add organic matter to the soil very effectively. Note that I don’t list buckwheat here, another great, fast-growing cover crop that bees love, too. That rhubarb and sorrel relative is not technically a grass or grain, though we think of it as such because of how we use it food-wise.
- Legumes (clovers, cow and field peas, vetch) with their inherent Nitrogen-fixing capability, provide Nitrogen effectively. Plus: you can even eat the leafy tips and blooms and young pods of field peas along the way, if you choose that one.
- Brassicas and Mustards (rapeseed or canola; radish; mustard) have proven effective against various nematodes, fungi and insects.
Cover crops—there are varieties for each season and each climate—also serve as a living mulch, protecting the soil from erosion. They thwart other weeds, making the management of fallow garden areas (such as during crop rotations) easier than just standing back and watching undesirable plants take over.
Even well into September, it’s not too late to plant winter rye here in my cold zone, as it will germinate as low as in the 30s, but I prefer to give it about four frost-free weeks if I can, so I just start as the beds come empty. I find that if I wait until the garden’s a blank slate it never happens, so it’s easier to just rake empty areas gently and then broadcast seed, covering it according to the individual crop’s directions.
Keeping a bag of organic seed or a mix of each of your chosen cover crops on hand insures you’re always ready (that’s winter rye blades and the just-germinated red clover, above).
If I had empty areas in spring I might use hairy vetch or oats or field peas here, or a convenient pre-packed mixture; in summer, I could use annual ryegrass or buckwheat, among others. Depending where you live, and what your purpose and timing is, here are some sources of high-quality seed, and a list of resources for more information below that:
- Hudson Valley Seed Library has organic, garden-sized single-ingredient or blended packages (like the one above). I was able to cover 1,000 feet, for instance, with oats and field peas.
- Johnny’s Selected Seed in Maine offers many varieties, including some organic, with a helpful chart for cross-comparison.
- Peaceful Valley, in California, has a selection for various regions, and a how-to video on cover crops.
- Bountiful Gardens, in California calls them “compost crops.”
- Cornell University has a tool for deciding which cover crop to use in your vegetable garden, plus articles on fall cover crops.
more information on cover crops
SOME OF THESE resources are geared to farmers, but have useful information on timing and how-to-grow tactics nonetheless.