Many gardeners think that only large-scale farms or vineyards can benefit from cover crops. However, even home gardeners are now recognizing the wisdom of growing these fall-planted crops. Not only are cover crops easy to plant, most types can just be ignored after seeding.

One of the primary reasons to plant a cover crop is to alternate the type of vegetation grown in your soil. Crop rotation not only allows us to diversify our harvest, but it also reduces the possibility of pests or pathogens gaining a foothold. 

Some cover crops, such as peas and fava beans, are even edible. These legumes are also nitrogen fixers, feeding the soil. However, they do not spread much, so inter-planting with ryegrass, buckwheat or another spreading cover crop is a good approach.

Cover crops can also serve as so-called “green manure.” Allowing them to grow over a season and then mowing or turning them into the soil can replenish nutrients. Legumes have long been used to add nitrogen to the soil after the grower harvests the edible peas or beans. As with all cover crops, roots left in the soil will decompose over time, improving soil tilth and structure. 

Winter cover crops also help gardens prone to erosion by anchoring the soil during the rainy season. What's more, cover crops suppress weeds. In many cases, a dense cover crop will out-compete undesirable plants, reducing time spent on garden maintenance. Some cover crops—winter rye, for example—produce chemical substances that inhibit some weeds. 

Tall grasses grown as cover crops can be mowed in spring and left to decompose in place, acting as a mulch and weed barrier. Alternatively, you can add fresh-mown cover crop residue to your home compost pile.

Clovers and buckwheat are not only attractive, but they also provide forage for bees and other pollinators. Cover crops provide a habitat for beneficial insects, helping reduce or eliminate the need for harsh pesticides later. 

Some cover crops act as traps, luring damaging insects away from your prized crops.  If you have herbivorous pets such as rabbits or guinea pigs, a cover crop such as alfalfa, once mowed, can be used as food or dried for bedding. 

For gardeners with heavy clay soils, cover crops can reduce soil compaction and improve soil texture. As the soil becomes more porous, other benefits follow. Better water retention, improved drainage and more biological activity—think earthworms—are all possible outcomes. 

A dense cover crop can also help shade the soil, a boon in hot or dry areas. Cooler soil requires less water because surface evaporation slows.

Suppressing weeds, feeding pollinators, controlling erosion and improving soil fertility are just a few reasons to plant a cover crop. However, cover crops must be managed or they can overtake a garden.  Mustard can reseed and multiply, effectively adding to your weed problems.

Nevertheless, the positives far outweigh the negatives. Even raised beds can benefit from the organic matter that a cover crop provides. As your garden activity slows this fall, consider trying a cover crop to prepare your soil for spring.

Workshop: U. C. Master Gardeners of Napa County will host a workshop on “Creating Holiday Wreaths” on Sunday, December 11, from noon to 3 p.m., at the Yountville Community Center, 6516 Washington Street, Yountville. Learn what plants in your garden could make good wreaths for decorating.  Learn how to choose and prepare plant materials so they will look good for a long time. Learn tips and tricks for designing and making easy wreaths for the holidays or any time. Participants will create their own wreath to take home, made from locally collected plant materials. $20 for Yountville residents; $23 for non-residents. Register with Yountville Parks & Recreation or call 707-944-8712.

Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.