What is old is new again, especially on the topic of cover crops. My father frequently mentioned that his Uncle Frank planted winter rye on the family farm in the Czech Republic in the early 1900s. Farmers and home gardeners have for many years utilized winter ground covers to minimize the effects of wind, frost and water on fallow soils. In recent years we have learned that ground covers are important for another reason: soil is alive, and cover crops maintain the microbial life essential to healthy plant growth.

Cover crops are called green manure because it is an efficient way to add nutrients to the soil. Winter cover crops are sown in the fall to grow during the winter, and are turned into the soil in the spring. Bare soil is losing its nutrients, especially carbon and nitrogen. Our plants and the soils’ microorganisms need nutrients, especially nitrogen to grow. Organic material (cover crops) help replenish the soils’ microorganisms in the soil for the next season of planting. Cover crops add organic material (carbon) to the soil, especially in the spring when turned into the soil to decompose, or simply mowed before planting. Cover crops also improve the soil’s structure by maintaining the soil microorganisms that help plants send their roots deeper into the soil. Good soil structure can hold onto moisture longer, especially in time of drought. Organic matter also contributes to better health and disease resistance of our plants.   Cover crops can be divided into legumes and non-legumes. Vetch and red clover are leguminous cover crops and their talent is to contribute more nitrogen into the soil when they decompose. Other winter cover crops are grains (non-legumes) such as oats, annual rye or winter wheat, barley, millet, mustard. Cover crops can also be used during the growing season as part of the vegetable crop rotation in your garden. Examples of summer cover crops are soybean, black bean, buckwheat. Chicory, comfrey, yarrow, nettles, and even dandelions are examples of perennial cover crops.   The most common winter cover crop is winter rye. Winter rye will remain green even under the snow, and will resume growth in the spring. However, for that reason winter rye can be a problem when it comes time to plant: it gets too big to be tilled under easily. And tilling creates another problem because it disrupts the microbial life that we are trying to protect. Winter Rye also has an allelopathic effect. It should be cleared totally out of the garden, preferably earlier than you plan to plant in the spring.   For all these reasons, raised beds (such as the beds at the Northampton Community Garden) are planted with a combination of oats and vetch. Both should sprout and grow even in the short cool days of fall. Oats will die back with hard freeze (though it may last until the ground freezes) and vetch will sometimes last even beyond that. But both will die back, and create a surface mulch that will protect the soil, yet enable spring planting with a minimum of soil disruption.