Sheet composting is a low-work gardening strategy that recharges your garden beds. The basic idea is that you create a layered compost pile on top of an existing garden bed or where you want to build a new bed and let the compost critters do the rest. Depending on what you put into your sheet compost, your bed will turn into mature compost within 6 months to a year. Fall is a great time to set up a sheet compost (also called lasagna compost) because it is easy to collect all the plant material coming out of your garden and off of your trees and pile it up on a bed rather than bag it for collection or haul it to your compost pile.
If you are building a bed on top of existing grass, or the bed you are composting has lots of weeds your first layer is corrugated cardboard. Overlap pieces of cardboard until you cover the entire area. If you need to plant the area before the cardboard breaks down completely, you can use a box cutter to cut an X in the cardboard big enough to fit your root ball. Wet the cardboard and then start layering on top of it. You typically want to top high-nitrogen “greens” with high-carbon “browns.”
Sheet compost to build new circular bed: cardboard covered with finished compost, cut grasses and topped with ornamental grass mulch.
Browns include dry leaves of any kind, newspaper, sawdust, wood chips.
Greens include grass clippings (avoid those treated with chemicals), green plant material, manure from herbivores, fruit and vegetable kitchen scraps, coffee grounds.
Manure is a great addition to sheet compost, if you have a good source for it, as it needs to compost for about 6 months before being used in the garden, which is exactly what happens in sheet composting.
If you have it on hand, adding layers of finished compost inside or on top of the bed can help the pile break down faster by introducing microorganisms. A top layer of finished compost, mulch or leaf mold gives the bed a finished look. You bed will be ready to plant come spring!
Sheet compost of cut hosta leaves topped with fallen tree leaves and leaf mold.