Garden cover crops for Fall

This being mid-August, I suspect most of you will soon be bidding farewell to the last of your spring vegetable garden, and if you choose not to try your hand at a fall garden, the soil will be left virtually bare. Bare soil is generally undesirable to the home gardener because of the possibility of erosion caused by wind and rain and the leaching of precious nutrients from the soil. The gardener’s remedy is a cover crop. Cover crops are crops which are allowed to grow in the “off season,” covering the bare ground with a thick mass of leaves and stems. These crops capture and hold valuable nutrients, preventing them from leaching into the subsoil and being forever lost. Then, in the early spring, this cover crop is tilled under or, in some cases, left intact, both to the benefit of the spring vegetable garden. Should you elect to go this route, it is time to be thinking about what type of fall cover crop you would like to plant in your garden. Cover crops are excellent soil builders. They afford gardeners several benefits. Most importantly, as previously mentioned, they make soil nutrients available either by “catching” soluble nutrients in the soil before they leach away or by producing nitrogen in their roots. Second, cover crops squeeze out weeds that sprout the same time they do and shade the ground, preventing the germination of many other pesky weeds. Third, cover crops improve soil structure (tilth). You may recall that in previous articles I have stated that any soil could be improved by the addition of organic matter. Cover crops, when tilled into the soil, add large amounts of organic matter. Some of them even create deep channels in the soil from which the roots of the crops which follow can greatly benefit. Finally, cover crops act as a protective blanket for the soil, preventing erosion by wind and rain. This is most important to our farmers but also to the home gardener. Following are descriptions of some of the most popular cover crops. One of the best is rye grain, or winter rye (Secale cereale). Rye is a very popular cover crop for gardeners because of its cold hardiness and heavy dry matter production. Rye will germinate at 33 degrees F, grows rapidly at temperatures between 40 and 65 degrees, and can even tolerate temps as low as -40 degrees F! Sow rye at the rate of 2 1⁄2 to 4 pounds per 1,000 square feet. Planting at least four weeks before the first fall killing frost allows it to get a fast start so that it can cover the soil well. Allow at least two weeks between plowing it under and planting the spring crop to allow time for complete decomposition. Annual ryegrass (Lolium multiflorum) is another good fall cover crop. It germinates readily at 45 degrees F and grows best at temps between 45 and 75 degrees F. Ryegrass is a totally different plant from rye grain, and since its roots are slower to rot, it should be tilled in earlier than rye in the spring. Be careful not to let annual ryegrass go to seed or it may become a weed. Sow at the same rate as rye grain. Wheat (Triticum aestivum) performs much like rye, except that it prefers 40 degree temperatures for germination and 45 to 85 degrees for optimum growth. Sow it at rates of between 2 1⁄2 to 4 pounds per 1,000 square feet and till it under at least two weeks before planting the garden in the spring. Sorghum-sudangrass, as the name suggests, is a cross between sorghum and sudangrass. Growing 5 to 12 feet tall, this hybrid produces large amounts of organic matter. This frost tender plant can be kept under control by mowing it to 6 inches tall when it reaches three feet. Buckwheat is a very fast growing broadleaf which is quite invasive, providing a quick canopy to shade out weeds. It matures in just 6 to 8 weeks, and can be planted between spring and fall garden plantings. Its white flowers can be used to attract beneficial insects and serve well as a filler in flower arrangements. Crimson clover is a nitrogen-fixing legume and thus helps to build rich soils. It also attracts beneficials, is quite attractive, and helps build good soil structure. Clover can be mixed with wheat or oats and broadcast across the entire garden. The small grains will germinate quickly and act as a nurse crop for the slower germinating clover. Other crops sometimes utilized as cover crops include vetch, Austrian winter peas, lupine, radish, turnips, and mustard. Cover crops are very useful tools for the home gardener who wishes to improve his soil’s structure and fertility. These benefits translate into bigger, healthier, and better-tasting vegetables. Try some!