A good mulch is especially important in the fall, not only to put the garden to bed for the winter, but also for its effects on the soil and the garden next spring.
Mulch is one of the gardener's best friends and one of the finest tools the gardener or groundskeeper possesses. It reduces labor and conserves water, and at its best can improve the looks and health of a garden, too.
Our use of mulches can be perfected by knowledge of their characteristics. Here are some of the most popular ones for use in the fall, and their effects on and uses in the garden.
Undoubtedly, compost is the Cadillac of mulches. Its beneficial effects on the soil are legendary, and it makes the gardener feel that he has, like Rumpelstiltskin, spun straw into gold. But
gardeners know that, like most of the best things in life, there is never enough of it to go around. Bulbs and flowering shrubs will benefit the most from compost applied in the fall.
For ornamentals, the leading mulch must almost certainly be shredded or chipped tree bark. Both look neat and have a nice, dark-brown color, but there are important differences.
Shredded hardwood bark is slower to break down in the soil, and absorbs many nutrients while doing so -- nutrients that would otherwise go to your plants. Its pH also tends to be acidic, and while some plants may relish this (e.g. azaleas, rhododendrons and blueberries), many do not. If you are using shredded bark, it is a good idea to check the pH of the soil and add lime to correct it if necessary.
Bark chips and nuggets, on the other hand, are usually pine bark. These are softer, break down more readily and are often easier to distribute neatly around smaller plants, like annual and perennial flowers and bulbs. As with all organic mulches, it also adds a nice tilth, or fitness to support growth, to the soil after it's been used for a few years (supplemented with judicious applications of fertilizer, of course).
Cedar chips are a mulch one occasionally sees at garden centers. I have used it in a pinch as a cover in winter for ornamentals and a vegetable garden. It keeps its light color for a long time, breaks down very slowly and probably is dandy used in permanent pathways. After two years, I am still unearthing nearly pristine pieces of it from my vegetable beds.
Leaves in the wind
Shredded leaves I have consistently found to be a clever idea with very little future, except in a woodland garden setting, where they are, of course, the mulch Nature intended. This is because they never seem to stay put, but toss about with every breeze; they extract great amounts of nitrogen from the soil in the process of breaking down, which is lengthy; and they tend to compact down in layers even when shredded and shed rain rather than absorbing it. They have their aficionados, but I am not one of them.
When mulching for winter protection of ornamentals -- trees, shrubs, perennial flowers and bulbs -- it is generally best to wait for the ground to freeze. One of the most important purposes of winter mulch is to prevent the heaving (and consequent breaking of roots and bulbs) caused by alternate freezing and thawing in the soil, or at least to minimize it. Four to 6 inches is a good depth for bark mulches. For straw, you can use between 6 and 12 inches.
Straw -- or if you're lucky, stable bedding, which is straw with manure mixed into it -- is also a very popular mulch for vegetable gardens. I am in favor of straw and stable-bedding mulches. They are biodegradable, improve the tilth and fertility of the soil, and look clean and neat.
Do be sure you get straw and not hay. Hay is often full of unwanted seeds of perennial grasses, since it is made from mature plants. Straw is the residue from harvested oats, wheat or other cereals.
Bedding straw from a farm or stable is ideal for a wintering-over mulch on ground where crops have been harvested. It will break down gradually over the season, and you can plant right through it in the spring, or turn it under, where it decomposes rapidly. Eight to 12 inches is not too much to apply in this case.
Grass clippings do not make a good winter mulch because they tend to break down very quickly when used in thin layers and to become moldy and go through anaerobic decomposition if laid down more than 1 or 2 inches thick.
Clippings from sprayed lawns should never be used, since the chemicals do not differentiate and will kill off vegetables and perennial flowers just as enthusiastically as they kill crab grass and Canada thistle.
Cover cropping -- growing any of a variety of plants with, or in rotation with, edible crops -- is a mulch option for the vegetable garden that deserves more use than it gets. Even for a very small garden it is well worth the small effort it takes to throw down a handful of seeds. The returns are disproportionately great.