Composting for a Productive Garden

Composting is the step that turns a garden from a series of purchases into a loop. A raised bed settles a few inches every year as organic matter breaks down, and it wants topping up each spring. You can buy that material forever, or you can make it out of what you were already throwing away.

The reason most first attempts stall is not technique. It is choosing a system that does not match the waste you actually produce. A kitchen-scraps household and a household with a big lawn and mature trees need genuinely different equipment.

Composting is a ratio problem. Greens -- kitchen scraps, grass clippings, coffee grounds -- are nitrogen-rich and wet. Browns -- dry leaves, cardboard, straw, shredded paper -- are carbon-rich and dry. A pile that is mostly greens goes slimy and sour. A pile that is mostly browns just sits there.

Aim for roughly two to three parts browns to one part greens by volume, and keep the whole thing about as damp as a wrung-out sponge. If it smells bad, add browns and turn it. If nothing is happening, add greens and water. That is genuinely most of the skill.

Home compost piles do not get hot enough, for long enough, to deal with meat, fish, dairy, oils or cooked food. Those attract rodents and go rancid. Leave them out of any open or static bin. A sealed tumbler is more forgiving, but the advice still holds for anything greasy.

Also leave out pet waste from cats and dogs, diseased plant material, and weeds that have gone to seed unless your pile genuinely heats -- most home piles do not, and you will be planting those weeds back into your bed next spring. The full list is in what to put in a compost bin.

An actively turned tumbler with a good ratio can produce usable compost in a few weeks in warm weather. A static bin you never turn takes six months to a year. A worm bin produces castings continuously once established, at a slower rate but higher quality. None of these is wrong -- they are different amounts of effort for different amounts of speed.

One to two inches across the surface of each bed, once a year in spring. On a 4 x 8 ft bed an inch is about 2.7 cubic feet and two inches is about 5.3 -- so a household with two beds needs somewhere around 10 cubic feet a year.

That is a useful number because it sets the size of the system you need. A dual-chamber tumbler producing a couple of batches over a warm season covers two beds comfortably. It also explains why a tumbler alone will not keep up if you are also trying to process a lawn's clippings and a tree's worth of autumn leaves -- that is a volume problem, and it wants an open bin.

• On soil rather than paving, where possible. Ground contact lets worms and soil organisms move into the pile, which speeds everything up considerably.
• In partial shade. Full sun dries a pile out; deep shade keeps it cold and wet.
• Level and reachable in bad weather. You will visit it with a bucket in the rain, and later with a wheelbarrow.
• Not tight against the house, and not under a window. Any bin gets opened on a warm day.
• Within wheelbarrow distance of the beds, because that is where the finished compost is going.

If you are starting from nothing, read composting for beginners, then pick a bin from the best compost bins. Finished compost goes straight back into the raised bed that started this, which is the point of the whole loop.