Cover Crop for Resiliency

July in the garden.

July is generally a transition time in the garden—most early crops are finished producing by early July and ready to be pulled out, opening up space for succession crops. We usually replace early peas, greens (bok choy, mustard, lettuce), and roots (radish, beets) with fall crops like broccoli, cauliflower, kale, carrots, bush beans, and daikon radish. In late August and early September, we’ll do one last round of succession planting for late fall/early spring greens. But for now, the steady rain the past few days has imposed a moratorium on planting. So, the garden is enjoying a growth spurt, and even in the middle of busy July, there’s time for a quick blog post.

Nothing stays the same

Spreading out the Garlic to dry before cleaning, braiding and storage.

Gardening is so unpredictable these days. Even the routine milestones that used to be consistent markers of the garden season can’t be taken for granted. We have always begun harvesting our garlic scapes (the flower stalk, which is typically cut off to encourage the plant to focus on bulb development, and because they’re delicious!) towards the end of the first week of June…sometime around the 5th–8th. This year, we didn’t harvest our first garlic scapes until the summer solstice, June 21. So, I wasn’t sure when to expect the bulbs to be ready for harvest, but they were right on schedule, even a little on the early side, and we pulled all 450 bulbs on Friday evening July 13, before things started to get wet.

How do we plan and prepare for such unpredictable garden seasons? The best strategy I can think of (in addition to working to change broader environmental policy and practices) is to build resiliency. We’ve been more committed to mulching, to mitigate against temperature and moisture extremes. We’ve long been using rain barrels to capture water. And, for many years, we’ve used a strategy more common to farmers than backyard gardeners—cover cropping.

Cover crops are a way to let plants do the work for us—they can prevent soil erosion and nutrient loss, attract pollinators, build nitrogen, add organic matter, and help control pest and disease problems. When you have a small garden, it can be hard to figure out how to incorporate a covercrop, because it means giving up food-growing space—cover crops are planted to feed the garden, not the gardener. And since it’s not a common backyard practice, it can be intimidating to figure out what to plant when.

Follow Garlic Plantings with A Midsummer Cover
If you grow garlic, you have an easy opportunity to start incorporating cover crops, because now is the perfect time for a mid-summer cover crop. And since you’ve just loosened the soil in harvesting the garlic, the prep work is already done. All you have to do is broadcast some seed, rake it in lightly and let the crop do the rest!

2013 photo of our raised bed vegetable garden.

Our main vegetable garden consists of long raised beds, 5’x25′ with 2′ paths in between. We plant an entire bed to garlic, fitting 450 heads (9 rows of 50, about 6” apart in all directions). About 80 of the biggest, healthiest bulbs get hung to save for seed for the fall planting of next year’s crop. That leaves us about 370 heads, enough for our two house collective of 12 people to use a whole head of garlic each day! And we do love garlic…but that’s also enough to share, and we often give some away.

Having an entire bed empty is a perfect opportunity to introduce a cover crop into our rotation. We choose a crop that will put on lots of growth by fall but is tender enough to be killed by the winter cold. When spring comes, we have a bed full of mulch ready for seedlings to be transplanted or for direct seeding larger seeds. It’s perfect for tomatoes or squash, which will also benefit from the soil improvements.

What to plant and how?
There are several options in the northeast, depending on your planting window what your goals are (weed smothering, erosion control, pest control, etc), but we always try to follow our garlic crop with a classic oat/pea cover. It’s a common practice to combine a nitrogen fixing legume, like peas, which benefit the soil but have dainty roots and don’t produce a lot of biomass, with a grass that does triple duty by providing support for the legume, holding soil with its mat-forming roots and providing lots of biomass for the compost pile, or to be left in place and used as mulch. Oat/pea is a great combination this time of year because there’s enough time for it to grow to full maturity—getting crops to flower—and be killed by the cold before setting seed.

Oats and peas 1 week after planting.

We harvested our garlic on a Friday night and had a heavy rain that Monday. The following weekend was busy with community events and my daughter’s 3rd birthday party, but when I saw a forecast of rain everyday for the next week, I knew a covercrop had to be seeded that weekend if it was going to happen before August. My 3-year old loves to help seed, and broadcasting cover crops, which doesn’t require a lot of precision (“Just make sure it goes in the bed and not on the path!”), is a perfect opportunity for her to help. So, between helping out at the Worker’s Center of CNY annual soccer tournament in the morning and attending the potluck before an evening house concert fundraiser being hosted at our collective, we aerated the soil with our broad fork (which she also loves helping me use), smoothed it out with the rake, scattered our seed, lightly raked it in and waited for the rain to do the rest.

Winter wheat and vetch being cut in early May.

Later in the season you’d want to choose a winter hardy cover crop, but it’ll mean more work in the spring. Winter hardy cover crops survive the winter and finish growing in the early spring. Once about half the crop is flowering, cut it off at the base and chop it up with clippers, letting it dry down into mulch, or dig it and turn the roots under, waiting a couple of weeks to plant so that incorporated plant matter has a chance to decompose. I’ve planted winter wheat or winter rye and hairy vetch (which gets a beautiful purple flower in the spring) as late as mid-September and seen good fall growth, excellent winter survival, and full maturity by early May. A good option to keep the bed covered for heat loving crops that won’t be planted until the end of May, but definitely not a good option for an area that’s intended for early spring crops.

Resources and Seed Sources
Fortunately, I had remembered to get seed this spring—sourcing cover crop seed (sometimes listed as “farm seed”) is not always easy. Locally, Lee’s Feed store often carries oats, field peas, clovers, rye, and wheat, but it’s not always in stock, so call ahead and ask. Online, Johnny’s, Fedco, and other regional seed sources are also great cover crop seed sources, carrying a wide variety, including premixed assortments, but shipping adds cost.

Oat and Pea cover crop mix.

Seeding rates listed by seed companies and on cover crop seed packets are often designed for farm scale planting, generally done by mechanical seeders. Broadcasting can result in less precise seeding and less consistent soil contact/coverage, and home gardens sometimes have more loss to squirrels and other critters. It’s a good rule of thumb to double the amount of seed recommended to get a good cover crop stand. For home gardens, you’re usually using a very small amount of seed anyway, given that this type of seed is generally sold by the pound. And it’s much cheaper to buy larger quantities. We often buy 5 lbs or more and store it in a cool, dry, dark spot to last for a few seasons rather than purchasing smaller quantities each year. I used about 1 ¼ lbs of a mix of oats and field peas to seed our 125 square foot bed.

Here’s a great guide to cover crops from MOFGA (Maine Organic Farmers and Gardeners Association) and a more local resource produced a few years ago by a Cornell graduate student to help community gardens incorporate cover crops. In fact, although it’s no longer active, her research, documented at The Garden Ecology Project, is still a great resource for gardeners.

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