Garden Like a Boss: Cover Crops
Get a jump on spring.
Within days of last month’s thaw, I was in the garden. Overwintered spinach and kale have repeatedly filled my plate and my belly. Some of the sweetest carrots I’ve ever had have been pulled straight from their winter slumber party. But while I have a handful of harvestable crops, there’s still plenty of bare, lonely soil just begging for some action.
Nature abhors bare soil, and will do her best to quickly cover it. I’m always keen to mimic her brilliance, and I always try to maximize every inch of sunlight that beams down from above. Plants are constantly pulling carbon from the atmosphere and pumping it down into the soil in the form of exudates to feed microbial life. Bare soil is being bombarded by UV rays, losing carbon and degrading soil life. Make sure you’re on Nature’s team and plant some cover this spring.
Serious gardeners are planting frost-tolerant cold weather crops now: spinach, peas, onions, radishes, broccoli, cabbage, kohlrabi and turnips. But our heat-loving favorites—tomatoes, peppers, cucumbers and more—won’t be planted for a full eight to 10 weeks. Now is a key time to reactivate your soil by planting that bare ground with cover crops.
Also referred to as green manure, cover cropping is one of the most powerful, yet underutilized techniques for the home gardener. Simply put, a cover crop is any plant grown for a purpose other than the garden’s usual output, food. Weed suppression, nitrogen fixation and increased organic matter are primary benefits. You can literally grow your own fertilizer and mulch layer with a well-timed cover crop planting, and planting now means you can make use of seasonal spring rains to get it done.
Select a quick-growing and frost-tolerant species. These will add biomass if we decide to “turn them in,” the process of chopping them just below the soil surface with a shovel, then lightly turning them under to bury them. They’ll be consumed by the microbes, worms, and arthropods, increasing organic matter and liberating the nutrients they once contained. If utilizing this strategy, make sure to allow a full two or three weeks after turning in a cover crop to allow for sufficient decomposition before following with another planting.
The second option is to “chop and drop” them, cutting them just below the surface of the soil with a shovel, then allowing the plants to remain on the surface as a great mulch layer. The roots that remain will serve to add organic matter and the above-ground foliage saves you the work of purchasing and hauling mulch.
For either of these techniques, the most effective time to cull the cover is when the plants first begin to flower (or two to three weeks before the following crop). Be extremely cautious about letting cover crops go to seed, lest their blessed vigor become a curse.
Even if you only get a modest amount of growth from these spring crops before turning them in, the benefits are well worth the effort of simply spreading a little seed.
Here are a few options for early spring cover crops. I tend to do a mix of all of them.
Spring oats: Oats are a quick-growing crop, excellent at scavenging nutrients and accumulating biomass. An excellent “nurse crop” for legumes (such as field peas), they create a symbiotic relationship when grown together. Oats can germinate in soils as cold as 38 degrees F, making them one of the earliest cover crops we can get in the ground. Oats do not tolerate heat.
Annual ryegrass: A quick grower and excellent weed suppressor, rye is fantastic at storing cycled nutrients and is one of my favorite cover crops to chop and drop. Rye performs well in poor soils and also as a nurse crop for legumes. Plant anytime the soil is at least 40 degrees F.
Field peas: Peas are a legume, a class of plant that fixes nitrogen from the air and banks it in the soil. The classic field pea is often a cow pea, sometimes a blend of several species, but any type of pea will work.
It’s often difficult to get a good crop of peas finished in time to follow with an immediate summer planting by Mother’s Day weekend. Indeterminate tomatoes, peppers and cucumbers aren’t a good choice to follow pea cover crops but faster crops like bush beans or determinate tomatoes would still have plenty of time. Beans are also legumes, so following peas with beans is a great strategy for maximizing nitrogen fixation.
Rhizobium inoculants for legumes are inexpensive and easy to use. They’re not always necessary in well-maintained soil, but if you haven’t broken your unhealthy addiction to the rototiller, you would be wise to treat your seed.
Aside from fixing nitrogen, peas break down incredibly easily once turned in, and the growing tops are edible as well.
Clover: Medium red clover or white clover is for those of you who need an “I’m traveling this summer and won’t have time to garden” solution. It is perennial, and provides the most benefit when allowed to grow into the second season. A legume, like peas and beans, it’s also fantastic habitat for beneficial insects and pollinators. Clover helps break up compacted soils, ruthlessly suppresses weeds once it is established, mines subsoil nutrients and is quite tolerant of shade. If you don’t have time to maintain your garden, you have the most to benefit from a clover cover crop!
James Loomis is the Green Team farm manager for Wasatch Community Gardens.
Artwork courtesy Mother Earth News:
Illustrations by Elayne Sears