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Crimson & Clover, Over and Over

Cover crops provide winter blanket
Clover cover crop at Agrarian’s hop farm. Photo by Trask Bedortha.
Clover cover crop at Agrarian’s hop farm. Photo by Trask Bedortha.

Hats off to gardeners who grow a fall and winter vegetable garden from seed. You have to get started at the height of summer, when watering and harvesting are at their most demanding. Sowing in situ is often impractical, so starts must be raised under shade cloth or in some cool part of the garden not occupied by summers’s heat-loving crops. 

September is too late to grow slower-growing crops from seed, but chard, escarole, lettuce and many other kinds of greens can still be seeded right where they are to grow. Kale is worth a try. It may not yield much of a crop this fall, but it should over-winter (and, in a mild winter, even grow a little) and it will take off fast as the weather warms again.

If I get some garden space cleared in time, I’ll plant purchased starts of purple sprouting broccoli this month, and maybe some Red Russian kale. This summer’s Tuscan kale should last through the winter, but I love the sweetness of Red Russian once the weather turns cold. Planting of onion and garlic starts can wait until October. 

I’ll also try to get some kind of cover crop going wherever I retire a summer crop. Mulching empty ground with autumn leaves reduces erosion and compaction somewhat, but a growing cover crop does a better job of conserving soil nutrients — and it looks encouraging, too. 

Crimson clover is a popular winter cover crop. Unlike some clovers, it’s an annual, so it won’t become a nuisance. It is hardy to about 10 degrees Farenheit, and (up until bloom time) the stems are easy to hoe into the soil. Crimson clover does not do well on very heavy soils or in places that may get waterlogged in winter. If this soundslike your garden, try Austrian pea. Steve Solomon (Growing Vegetables West of the Cascades) suggests pulling out the long, wiry vines in spring for composting rather than trying to dig them under. I sowed some Austrian pea last fall. It proved to be very cold-hardy, and I enjoyed eating the sweet young shoots in winter salads. 

Cover crops that are also edible make a lot of sense. Fava beans (Vicia fava) are a classic. They can be sown late September through October, or in very early spring if you miss the boat. I eat the young tips in winter and leave some plants in the ground for a fresh bean crop in early. Last winter was hard on fava beans, but my Broad Windsors squeaked by under the snow, sending up a whole new set of shoots from below ground and cropping right on time. 

If you don’t want beans from your favas, you can sow the small-seeded bell beans or any hardy fava and hoe them into the soil while the stems are still soft. Some gardeners swear by fava beans for improving heavy soils, but they don’t like it wet. 

All of the above are nitrogen-fixing legumes, so even if you remove the top growth in spring for composting it’s worth leaving the roots in the ground to release their nitrogen. Solomon suggests taking full advantage of that nitrogen by planting early greens directly into the fava bed, after some shallow hoeing. 

When I am busy my favorite quick reference for what to plant and when is The Timber Press Guide to Vegetable Gardening in the Pacific Northwest by Lorene Forkner. But I also like Solomon’s deeper narrative style, and he has a lot to say about his preferred cover crops. Toby Hemenway, in his book Gaia’s Garden, has a comprehensive table of cover crop plants, listing their seasons, soil tolerances and strengths. The purpose of cover crops, he says, is to build and hold soil and to smother weeds. The roots of a vigorous cover crop like canola and mustard can punch through clay and hard subsoil, driving down deep to loosen soil and draw up nutrients while leaving new organic matter far down in the soil. Green Wave mustard is a favorite of Carol Deppe, author of The Resilient Gardener and a fan of multi-purpose crops. 

For small areas in need of a winter blanket I favor lamb’s lettuce (aka mache, corn salad or vit). It is astonishingly hardy, and the succulent, tender, deep-green leaves form the basis of months of winter salads. Only a few inches high, it is easy to grow around taller over-wintering crops. Native miners’ lettuce can be used in the same way. Both these, along with chickweed, will happily self-sow wherever you tolerate them, becoming a default cover crop that will feed both you and your soil.