composting 101

HERE, IN THE COMPOST HEAP, is life and death and life again—proof positive of “from dust to dust.” But too many gardeners waste the raw material of future soil amendments by getting hung up on silly details, like what shape of pile or kind of bin to use, what can and can’t go in the pile, or how much work they fear composting will be. It doesn’t have to be much work at all; even without turning and other human intervention, the leaves on the forest floor break themselves down in time, don’t they? So will your pile, if it’s made sensibly.

What method of composting you use should be determined by the volume of material created in the yard (and to a lesser degree, in the kitchen, where vegetable scraps, egg shells and coffee and tea grounds can be collected for the heap, too). I create far too much raw material for a mere bin-type system, the commercially available kind made of metal or heavy plastic or mesh that are about as big as a washing machine. I have one of those, a metal one that shuts tight and thereby keeps animals out, to hold my vegetable food wastes, alternating them with layers of garden debris and a little soil or finished compost to get things activated and reduce any chance of unpleasant odors.

The latest rage is all about lobster-trap-wire bins, meaning really durable even under the ocean day in and out. But my main heap is about 40 feet long and 5 or 6 feet wide, a long, open pile that in composting jargon is called a windrow. In the peak of fall cleanup and leaf raking, it gets to be about 5 feet tall, too, but as the material begins to settle, and eventually to break down, it’s usually more like 3 to 4 feet high.

Whatever style of composting you choose, from a simple, small pile to a long windrow to an enclosed store-bought bin, the key is to vary the kinds of materials that go into the mix. There is no precise recipe; there is just common sense at work here, too. Green plus brown equals black gold. Layer the two basic categories of ingredients: green ones (nitrogen-rich materials such as grass clippings and leafy green plants) and brown ones (carbon-rich materials like dry, brown leaves or twiggy bits and pieces). Too much of either one will impede decomposition.

I liken successful composting to the combustion that goes on when my car is running smoothly: to ignite, the car needs fuel, air, and a spark. So does the compost heap. The spark is the nitrogen-rich green stuff; the fuel is the brown stuff; the air is supplied by occasional turning of the pile, and water must be available from rain or the hose, so the pile is slightly moist but not sodden.

Too much green stuff (particularly wet things like grass clippings) will produce a smelly heap; spread them around, and toss in a thin layer of soil or old compost to help things get going. I don’t bother with store-bought compost starters; there are plenty of beneficial micro-organisms in good garden soil and some well-rotted leaves. Too much brown stuff will just sit there (and that includes things that are “brown” chemically if not in color, like piles of orange rinds from weeks of juicing). Chopping up difficult brown elements will speed decomposition; so will aerating the pile, and adding more greens. And don’t site the heap in the dark; a position in at least part-day sun is essential to good decomposition.

It’s easier to list what doesn’t go in the heap than what does. Leave out weeds with seeds on them (pull them before they go to flower and seed, when they can be composted); weeds that spread even without seeds (like bulbous onion grass); diseased plants; fats and oils, such as dairy products and meats and fish; bones. Manures from farm animals (not domestic pets) are great additions to the heap, if you can get them from a nearby farm or stable, but remember that unless they are well-composted in a fast-decomposing (or “hot”) pile, between 120 and 160 degrees F, they will be full of the seeds of what the animals were fed, so plan to let them rot thoroughly in a heap that’s really cooking along. A compost thermometer will help eliminate the guesswork here.

That said, I will admit I put most weeds in my heap (not bagging them up for the trash) and that I never take my heap’s temperature. Nobody is perfect.

A PLACE JUST FOR LEAVES

If you want to use compost as mulch later on, I recommend composting leaves separately, in their own pile. They can be shredded to speed up the process; this can be done if they are raked into small piles where the heap is to be made and run over with the mower, which works better when they are dry. Then moisten the pile and perhaps sprinkle in some soil or old compost. The leaves can also be left whole, in bags or in a pile, all winter and shredded come spring. Leaf mold, as the rotted stuff is called, is a great mulch or soil amendment.

How often you turn your pile will affect the speed at which finished material is ready to be returned to the garden; if you’ve got time, you can escape turning and just let nature take its course (again, nobody’s perfect—and would you like to turn a 40-foot-long windrow every few weeks?). I turn twice a year, in spring and late summer or fall, and extract the lowest layer, where the finished stuff is hiding.

After 20 years of doing this by hand, I recently treated myself to a small tractor with a front-end loader, and the work will be easier from now on. Before using the compost in the garden, I toss it through a homemade sifter, into a wheelbarrow, to cull the stones and sticks and unfinished bits like tenacious corncobs or thick roots. I top-dress my flower beds with an inch or two of the sifted material each spring, along with some all-natural organic fertilizer, and use the rest to top up my raised vegetable-garden beds. Yummy.

Favorite Resources: I am as proud of my compost heap as I am of any part of my garden. It is the archaeological record of my garden past; it is the stuff from which future gardens will arise. I read a lot about, from sources like these: Garden Organic, a 50-year-old British charity; Journey to Forever (don’t worry, not some into-the-bunker survivalist cult); and the vast Cornell Composting archive. Dig in.