Integrating cover crops into your design plan

Crimson clover. Source: Wikimedia Commons.
Crimson clover. Source: Wikimedia Commons.

For a long time, I was confused by cover crops.

Cover crops are seeds that are planted to build and protect the soil. Rather than producing an edible harvest, the purpose of cover crops is to give your garden a rest by replacing some of the nutrients and organic matter that your greedy veggies depleted over the growing season. Cover crops also suppress weeds, prevent winter soil erosion and loosen compacted soil. They need to be killed and composted before they set seed (otherwise, they’ll self-seed, mature and turn into a lawn) by mulching, digging in, or letting frost do its work. Then, after giving a few weeks to let it break down, your bed is ready for planting again.

Cover crops fall into a few broad categories: soil-builders, nitrogen-fixers and pest-controllers. Soil-builders include buckwheat, rye, oats, wheat and other grains. They grow quickly and add large amounts of organic matter to your soil. Nitrogen fixers include clover, fava beans, hairy vetch and other members of the legume family. They attract rhizobium bacteria to their roots, converting atmospheric nitrogen into a form that plants can use. Pest-controllers include alyssum and white mustard, plants that attract beneficial insects and are noxious to pests. Choosing the right cover crop depends on your goals, but for most people, mixing up a “cocktail” of a soil-builder and a nitrogen fixer will do the trick.

Still with me?

For years, no matter how many courses I took or books I read, I didn’t understand how to incorporate cover crops into my relatively small growing space. Cover crops take up a lot of room and really don’t do well with interplanting. I knew that cover crops are very important — they are one of the cornerstones of sustainable food gardening — but I just couldn’t wrap my head around how to make use of them. Since my garden is managed intensively, with fresh crops added successively, planting a cover crop felt like an annoying sacrifice of precious growing space. I thought of some crazy ideas, like growing pea shoots as a cover crop so that I could at least get some food out of the equation (actually, I still want to do this), but I still didn’t take much action.

This year is going to be different. I’m incorporating cover crops into my design plan.

Of our six garden beds, I’m planting one with a fall sowing of crimson clover, a nitrogen-fixer that has beautiful red flowers that bees love (our soil is already full of organic matter, so I’m skipping the addition of a soil-builder). This cover crop will go into a bed I most recently used for a three sisters planting — heavy feeders (except for the beans, which are themselves nitrogen fixers) that keep going until the very end of summer. I am going to clean the bed out entirely, and will then plant the whole thing with clover.

Why is this a good design practice? Well, aside from the benefits to the soil, I’ve reluctantly realized that *not* planting a winter crop on every square inch of my garden has its benefits. Most of the overwintering seeds I’m sowing now, like spinach and lettuce, won’t be harvestable until mid-April. But, in the meantime, I know that I’ll be itching to start planting new seeds by mid-March. Intentionally holding aside one bed will keep me from overplanting. The bed I planted with the cover crop will be the very first thing I tackle in the new year.

My new rule of thumb is: if you have several beds or planters, reserve one for a cover crop, and plant the rest with overwintering veggies.

You can order cover crops from your local seed company — I used West Coast Seeds. In general, cover crops get planted thickly, so you’ll want to buy a larger amount than you would with your veggie seeds. Cover crops can be planted at almost any time through out the year, though you generally want to get them in before the first frost. I’ll be planting my clover soon.

Good luck!

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