The summer growing season always produces lots of surplus green material for composting. This includes grass clippings, weeds that have not gone to seed and spent annual plants. The fall, conveniently, produces lots of nice brown ingredients, in the form of dead leaves.
We have, therefore, the green and brown makings of a fine compost pile. But if you have a vegetable or flower garden that is essentially bare, with all the annual plants removed, you can let nature make compost for you right there. No piling, no turning, just spread it and forget it.
This is called sheet composting. The billion little critters in the soil lose some members in cold weather, and those that remain may slow down somewhat, but they still like to eat. Take those green and brown materials, shred them a bit with a chipper-shredder or by running over them with a bagging lawn mower. Then spread them evenly over your garden. If you listen very carefully, you will hear a chorus of cheers as the decomposers move in and start chomping.
Sheet composting helps all forms of soil life, from beneficial bacteria to big beetles, everything in between, and of course lots of earthworms. Through the winter, you can continue to toss scraps of vegetable waste (preferably chopped, but they'll deal with it however it comes) to sustain your army of garden helpers. These are the critters that make plant nutrients for you.
If you have enough, this blanket of vegetative matter will protect your soil as a useful mulch. You can of course add actual compost that has already begun to break down, since this is teeming with decomposers that will happily spread out and multiply as they deal with the less-digested material.
By spring the sheet of compostable material will have broken down enough to be incorporated lightly into the top few inches of soil. My favorite tool for this is the three-tooth cultivator designed by Eliot Coleman and sold by Johnny's Selected Seeds (johnnyseeds.com). Do not use a rototiller, and do not dig or (worse!) double-dig it in. All that sheet-composted material is still teeming with soil life, which will benefit your plants if it is at the same level as their roots. Tilling and digging puts it too deep, and brings weed seeds closer to the surface, where they can haunt you as the weather warms.
PETER GARNHAM grows his gardens on Long Island, New York. He is a Master Gardener and a contributing editor for Horticulture.