Hill Gardens of Maine - Ground Covers & Living Mulches

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Ground Covers & Living Mulches
by Fred Davis, MG, Hill Gardens, Palermo (To view other previous articles, click Archives)

Welcome through Fred's Garden Gate! The halfway mark has come and gone and it's time to give some thought to the bare spots that are beginning to show up in the garden. As vegetables are harvested and the now-fruitless plants and vines are removed to the compost pile, the remaining weeks before hard frost could be crucial to the real success of next year's crops.

Even if some compost and a load or bag of manure was applied at the beginning of the season and plans are in place to do the same next spring, there's something important that good gardeners everywhere know that can be done right now to further enrich their soil. Consider these points:

Soils left unprotected through winter are vulnerable and subject to wind and water erosion...that means loss of topsoil which ends up on some far-off mountainside or in the neighborhood pond or lake. Maine soils contain significant amounts of phosphorus which, when combined with already high levels in our lakes, means further long-term damage to a precious resource.

Stones and gravel don't blow or wash away--organic matter (humus) and nutrients do...so unprotected soil gets poorer with each passing season, requiring more artificial nutrition. Cover cropping, as the name implies, prevents wind and water erosion.

Cover crops ("green manure" when tilled in) return important elements to the soil at the very peak of nutritional value. These elements are held in place by the organic matter which contains them, to be released to the new crop next season. Additionally, legume cover crops like clover, peas, alfalfa and soybeans have the ability to accumulate and store nitrogen.

The deep and vigorous root systems of some cover crops penetrate and loosen compacted or clay soils. As these roots decay, thousands of tiny tunnels filled with humus allow more thorough absorption of water and facilitate the passage of air.

Finally, the young, fresh and succulent leaves and stems of freshly tilled-in green manure decomposes much more rapidly than the older, dried-out material in compost or stable or barnyard manure. It is therefore possible, in our area, to grow and plow-in two successive crops. What wonderful things that'll do for depleted or abused garden soil!

BUCKWHEAT is probably the most common summer and fall cover crop. It is fairly coarse, can grow waist-high very quickly, is an excellent bee plant and has a vigorous root system well suited to deep penetration into subsoil. It should be sown as soon as possible after harvest. I'd suggest tilling it in when it reaches 12 or 14 inches and replanting a second crop to remain over winter. If buckwheat is allowed to grow to maturity and flower, it is far too coarse for the average home rototiller and must be mowed or bush-hogged before tilling.

WHITE SWEET CLOVER, a nitrogen-fixing legume, prefers a soil to which lime has been added. It is fast growing and can be tilled under in the fall before its seeds mature. White sweet clover is an annual so it won't try to take over your garden.

WINTER RYE is well suited to poor Maine soils and continues to grow right up to frost. It is a perennial and will survive even the harshest New England winter. Plow it under in the spring as soon as the soil can be worked.

Seed of these cover crops is readily available at most farm and garden stores along with advice on how much you'll need for a given sized plot. Give some serious thought to cover-cropping your garden this and every year. Tilling in a crop of "green manure" makes a whole lot more sense than buying bags of fertilizer or shoveling a truckload of manure next spring! And you'll reap a better, healthier harvest in the bargain.