In the compost pile, green and brown make black gold

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We have a saying at our house: “The compost pile is just another mouth to feed.” After all, our garden thrives on compost, and thus we thrive on it, too. That pile is an energy center, like a furnace, and the closer it is to the house, the more easily we can stoke it.

If you’re an urban dweller, your compost pile may have to be discreetly concealed and rodent-proofed with wire mesh or some other well-aerated structure. But it’s not an object of shame. Unlike your town’s landfill, it doesn’t contain indecomposable plastic items or toxic chemicals. Everything in it was once alive, and through the transformative work of bacteria and other organisms, it will live again in the form of plants it has fed. Much of what goes into the pile has been discarded, yes, but we prefer to call it repurposed. Give it an honorable discharge and a new job.

Compost materials are plentiful in summer. The weeds we pull and the grass we mow could easily fill the pile to overflowing, and, after it settles a bit, fill it again. But with compost-making, variety is more important than volume.

Most compost ingredients fall into two categories: green and brown. The moist, green ones are nitrogenous (high in nitrogen), and the dry, brown ones are carbonaceous (high in carbon). Put them together, and they’ll stir up heat, with carbon as the fuel and nitrogen the flame.

Both must be in balance, though. An all-green pile breaks down too fast, as the nitrogen volatilizes. It smells foul and burns crops with its caustic heat. An all-brown heap, by contrast, would ultimately break down, but very slowly. So the trick is to add some green materials, then a layer of brown ones, then green again - as if you were making a high-rise sandwich.

The composting process involves chemical reactions, but it’s a physical process, too. Brown ingredients such as twigs, straw, crisp oak leaves, cornstalks and dead bean vines hold the particles of wet, sloppy green matter apart, with air in between. That’s essential, because the microbes that do the job are aerobic -- they need air. And an active, well-balanced pile will not smell.

Always keep diversity in mind. During the green time of year, you might have to look harder for brown ingredients. In fall, or in a severe drought, there’s lots of crackly brown stuff but not much lush green. Turning the heap from time to time will help keep it active, as will moistening it at times when no rain falls. But if the heap is layered in a balanced way, you can avoid all that work.

A wide variety of materials pays off in other ways. Each brings its own biological and mineral package to the table. Maximum variety leads to a more complete nutritional package for your plants (and subsequently for you) when finished compost is added to the garden.

Most nitrogenous materials are literally green -- weeds you tossed in (avoiding those with viable seeds), lawn clippings, bolted crops such as yellow-flowered broccoli and towers of lettuce, the arugula you ripped out because the flea beetles got to it, and great zucchini torpedoes, chopped up for speedy action. But they also include red apples too marred to eat, the blossoms you deadheaded in the flower garden and the houseplants you forgot to water or drowned. These aren’t failures or trash. They’re simply moving on to their next role.

Food scraps such as banana peels, orange peels, potato skins and eggshells will be devoured by the compost pile, along with the past-expiration-date matter you find in a fridge purge (no oil, meat, fish or dairy products). Burned the rice? Pass it along for its reincarnation as fertile soil. From garbage comes black gold.

At times when brown stuff is scarce, a few bales of straw or spoiled hay are great to have on hand. If they’re not available, use hedge prunings, sawdust, wood shavings and even pieces of cardboard. Paper filters can be tossed in with the coffee, tea bags with the tea. Old pillow stuffing is fine if it’s cotton, feather or down, but not synthetic. So is the occasional newspaper, especially if it’s fresh from the hamster cage.

Manure, especially from horses and cows (never cats and dogs) is a good, balanced compost booster. Crab and lobster shells, fish, seaweed, and other ocean-sourced materials break down easily and are rich in minerals that plants need.

When you pick potato bugs or Japanese beetles off your plants, drown them in a jar of water, not soapsuds, kerosene or anything you wouldn’t want in your soil. Then commit them, respectfully, to the wheel of life.

- Damrosch is the author of “The Four Season Farm Gardener’s Cookbook.”

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