A Guide to Compost and Mulch
by Paulette Mouchet
Originally published in The Rose Garden newsletter, September, 2002
For those who long for an easier way to garden, compost and mulch hold the key. Compost and mulch can be used in similar ways in the garden, which leads to some confusion, especially among beginners.
Compost is vegetative material that has been decayed or rotted. Gardeners call the decaying process composting. Decomposition generally occurs two ways: hot method or cold method. In the hot method, the vegetative material generates a lot of heat as it rots. This kills weed seeds and most diseases and microorganisms, including beneficial organisms and earthworms. Compost piles that are hot generally decompose faster than those that are not.
With cold composting, the vegetative material does not create heat. Worm composting, or vermicomposting, is an example of cold composting. Cold composting generally takes more time than hot composting and does not kill weed seeds or microorganisms.
Finished compost is crumbly, light in texture, dark brown, and smells of good, rich earth. Earthworms love it, as well as other beneficial soil inhabitants. Compost can be tilled into the soil as an amendment or applied in a layer on top of the soil as mulch.
Mulch is "stuff" spread on the surface of the garden to choke out weeds and help the soil retain moisture. In the summer, a thick layer of mulch helps keep the soil cool; in the winter, it helps keep the soil warm. "Stuff" commonly applied as mulch includes horse or cow manure, straw, alfalfa hay, seaweed, grass clippings, wood chips, leaves, shredded bark, pine needles, and shredded newspaper.
Mulch can be either uncomposted material such as fresh grass clippings, fresh manure, or alfalfa hay; or finished compost such as homemade compost or purchased redwood compost. Some materials work better when they are composted before being spread as mulch. For example, most folks prefer to use composted horse and cow manure as opposed to fresh manure.
Experienced gardeners have found that using a variety of mulches and composts is good for the garden in the same way that eating a variety of foods is good for humans. Mulching is one of the most important things you can do for your garden.