Many people see fallen leaves as a mess to be cleaned up and discarded, but I see them as gardening gold: compost!
Compost is organic matter, or humus, that helps build good soils. It improves tilth (a fancy word for crumbly, earthy-smelling soil) and holds nutrients and water near plant roots. Compost feeds the beneficial insects and microbes that help plants grow and fend off pests and disease.
Composting is the controlled process of turning yard waste and other organic materials into this valuable soil amendment.
Nature makes compost by breaking down dead plant material using organisms such as insects, fungi and bacteria. Master a few simple concepts, and you can make your own compost.
Composting is like cooking. Your ingredients go together in particular ratios and then “cook down” with occasional stirring. The primary ingredients are “browns” and “greens.” Browns are dead plant materials high in carbon and low in nitrogen—fallen leaves, small sticks, wood chips. Greens contain higher amounts of nitrogen. Some are obvious, like fresh grass clippings and vegetable scraps; others can be surprising, like manures and coffee grounds. Compost starters and other additives are typically unnecessary.
Start with a pile. Making 4- to 6-inch layers, blend approximately equal volumes of brown and green materials. To “season,” you can add a shovel full of garden soil or finished compost to inoculate the pile with essential microbes.
If your materials are dry, you may need to sprinkle with water as you go to keep pile contents damp but not wet. Test the moisture by squeezing a handful of the blended materials. It should yield one to two drops of liquid. If it doesn’t, add water. If it yields more than a couple drops, add dry materials. Keep layering and blending until your pile is about 3 feet by 3 feet by 3 feet. Smaller piles will dry out quickly, hold less heat and compost more slowly. Piles larger than 5 cubic feet will be difficult to turn and have a greater chance of turning anaerobic, spoiling and yielding bad odors. For best performance, locate your pile out of direct sunlight.
It’s not essential, but you can build or buy a bin, cage or other container to keep your pile from growing too large or spreading out too thinly.
Even if you do nothing else after your pile is built, compost will happen! We call this “slow composting.” It may take from six months to two years, depending on temperature and moisture, to become finished compost. As it decomposes, the pile will shrink. Feel free to add more ingredients from time to time. Stir it up once a month or so to mix the materials, aerate the pile and prevent it from souring.
Want to speed up the process? The basic recipe is the same, but “fast composting” requires you to turn the pile much more often—every three to five days during the summer, less often in the winter. Make sure the pile stays damp, and let the pile go through a “heat” after each turning to kill weed seeds and potential diseases. This process can yield finished compost within two months.
You’ll know your compost is finished when it is dark and crumbly and you can no longer recognize what it used to be. At this point, it is the perfect soil additive.
S. CORY TANNER is an area horticulture agent and Master Gardener coordinator for Clemson Extension based in Greenville County. Contact him at shannt@clemson.edu.