Compost is “finished” when you can no longer recognize the ingredients that went into making it because they have thoroughly decomposed. It looks like dark, fertile soil, only fluffier, enriched and lightened by the work of bacteria and other soil organisms at work inside your compost pile.
That’s the general standard of compost quality, but in fact there is more of a gradient - more stages at which decomposing organic materials can be of use to the gardener.
An extreme example is sheet composting, in which organic materials are spread over the ground, where they will eventually break down and improve the soil beneath in the long, leisurely way that nature practices, when branches fall from trees and the leaves of summer wither and rot.
For years I’ve been composting garden debris by strewing it over a wedge-shaped grove near the garden. Trees were planted there 15 years ago as a windbreak and privacy screen, but the soil was never great. So wheelbarrows of pulled garden weeds are sometimes dumped there, along with tall perennials I cut down in the flower borders in the fall. Their gradual decomposition will help those trees.
There’s also a use for what I call rough compost, from a casual pile of plant matter that hasn’t yet reached perfection but has settled and softened enough that you can shovel it into a cart and then till or spade it into the soil. It will go to work more quickly than sheet compost but not as fast as No. 1 Finished Grade A Prime.
How perfect can perfect be? Some composts are better made than others. If you have balanced your pile, alternating fresh, moist nitrogen-rich ingredients such as green weeds, manure and kitchen scraps with dry, high-carbon stuff such as dead pea vines and hay, so that the pile heats up, it will be just right. If you then turn it inside out, to cook it more evenly, it will be better still.
But there is a stage beyond that: sifted compost. Putting the compost through a sifter will not increase its potency, but it will create a fine texture, breaking up moist clods and removing unwelcome items such as stones, bones and chunks of wood.
There are several uses for sifted compost. This fall I renovated a section of lawn, removing patches of weeds, scratching the soil up with an iron rake and reseeding as needed. I then loaded a wheelbarrow with sifted compost and used a shovel to fling it across the roughed-up places, to help new grass establish itself in the spring.
Sifted compost is also great as a medium for plant containers, in combination with peat moss. Use it when bringing herbs indoors in winter, for moving a houseplant to a bigger potand for giving spring transplants such as tomatoes a luxurious temporary home.
When direct sowing, fill a furrow into which you have dropped peas, beans or other seeds, so that nothing will impede their growth. If your garden’s soil is rocky, heavy, compacted or otherwise daunting to a picky root cropsuch as carrots that balks at any obstruction, you might fill a trench with sifted compost - or even sifted soil. The carrots will be in heaven.
So how do you accomplish this feat? There are sifters for sale, but anyone can make one. Yes, you! Cut four lengths of 2-by-4s and screw them together to make a rectangular frame that fits the top edge of your wheelbarrow as closely as possible. Cut a square of half-inch hardware cloth (or quarter-inch for a finer texture). Screw 1-by-2 strips of wood to the top of the frame with the hardware cloth in between, to hold it in place.
Place the frame over the wheelbarrow, drop a shovelful of compost on the frame, and shake it back and forth, with the 2-by-4s sliding on the wheelbarrow’s top edges, so that the material falls through the mesh. You can also use your hands, in sturdy rubber gloves, to work the compost through. If any degradable compostable items remain intact - thick cornstalks or cabbage stems, perhaps - just toss them back onto the compost pile and give them another year.
Damrosch is the author of “The Four Season Farm Gardener’s Cookbook”; her website is www.fourseasonfarm.com.