By Barbara Perry Lawton
Stuff rots. That, in essence, is the principle of composting. And when organic matter rots, it becomes a wonderful material that, when worked into your garden soil, greatly improves its structure and slow-release nutritional value. Compost also adds life to your soil in the form of beneficial microorganisms such as bacteria, fungi, as well as beneficial earthworms and insects.
Interestingly, compost will improve the drainage and aeration of heavy clay and also will increase the moisture-holding capacity of sandy soils. In other words, no matter what your garden soil is like, adding compost to it will make the soil healthier for garden plants as well as easier to work. Composting is so easy that I’m always surprised to find gardeners who do not compost their garden and kitchen waste.
Materials for composting include garden clippings, weeds and kitchen scraps. But never compost garden waste from diseased plants or weeds that have gone to seed, and never include meat scraps, fats or dairy products in your compost heap – only healthy plant materials. Kitchen scraps with good composting qualities include coffee grounds, vegetable peelings, salad scraps and similar materials.
Don’t rake lawn clippings—they are better left in place where they will provide as much as 25 percent of the nutritional needs of your turf grass. If a freshly cut lawn has large clumps of grass (was the grass wet or very tall when you mowed?), you can add a layer of that to your compost heap – it’s better if it’s on the dry side.
Consider composting materials as brown and green. Brown, of course, would include fall leaves, twigs and similar stuff. The green materials are green leaves, weeds and so forth. A workable rule of thumb as to the ratios of materials to compost is to have roughly equal amounts by weight of brown and green materials. That would equate to approximately half brown and half green by quantity. With the right ratios of materials and moisture, you will have a hot compost pile, one that will decompose quickly. But even cool compost will eventually rot into a lovely fertile material for use in amending your soil.
Once compost is piled up – no higher than three feet – it should be kept moist but not wet. Taller piles of compost may decompose anaerobically, which produces ammonia that can cause unpleasant smells and may well harm plants. The rate at which the compost rots will depend upon the temperature, moisture content and consistency of the compost. Compost made up of finer materials will, of course, decompose more quickly than coarser materials. Turning the compost every couple of weeks will speed up the process.
Where to Put Compost
If you have plenty of yard space and a secluded spot, you may wish to just pile up the yard and kitchen waste. On the other hand, you may wish to construct or buy composting bins. If you have three, you can have compost in three stages of decomposition, a plus for those who have a number of beds and borders. There also are specially made composting tumblers that allow you to crank the container, thus turning the compost easily.
Since my gardening space is comparatively small, I try to sheet compost all my garden trimmings. By this, I mean that I put the garden scraps directly back into the garden beds, allowing it to rot in place under the plants. This process, sort of a cross between composting and mulching, is rather like that which happens naturally in forests – the leaves and twigs decompose in place rather than in a special pile. If you cut up the trimmings into small pieces, it’s amazing how much garden trash can go right back under the perennials and shrubs. Don’t let the sheet composting pile up any higher than four inches.
If you compost in bins or piles, eventually you will end up with a rich dark crumbly material called humus. You have returned organic matter to a form that will enrich your garden soil tremendously. Humus as a material itself, the product of disintegration of organic materials, is poorly understood scientifically.
We know that humus can greatly improve soil structure. We also know, according to William Bryant Logan in his wonderful book Dirt writes that “(humus) is the habitat for a diverse microflora and microfauna that tend to suppress or eliminate disease organisms, in order to continue their own robust lives.”
Composting is easy, good for your soil and your plants, and offers a method for getting rid of garden waste. Experts suggest that as much as three-quarters of our household waste is made up of organic materials that could easily be composted. With landfills filling up at an increasingly fast rate, composting offers a win-win situation that is good for us and good for our communities.
Barbara Perry Lawton is a writer, author, speaker and photographer. She has served as manager of publications for Missouri Botanical Garden and as weekly garden columnist for the St Louis Post-Dispatch. The author of a number of gardening and natural history books, and contributor to many periodicals, she has earned regional and national honors for her writing and photography. Barbara is also a Master Gardener and volunteers at the Missouri Botanical Garden in St Louis MO.