Mulching is nature’s recycling system. Nature spreads thin layers of organic materials evenly over the surface of the soil. Year after year, season upon season, leaves and blades of grass mature, die, and fall to the ground. Soil organisms begin the process of decomposition. First molds, then bacteria, later earthworms and beetles all come to return organic matter back to the soil from which it came. In this process of natural mulching, topsoil is gradually created over time. Rich layers of humus—decomposed organic matter in the soil—are formed that give the soil its dark color and good rich-earth smell.

You may find it surprising that the first bit of advice is to avoid composting as much as possible by learning how to mulch various organic materials. Mulching simply refers to any technique where organic matter is spread in thin layers on the surface of the ground and left to decompose naturally so that soil organisms can convert it to humus. Decorative bark layered around shrubbery is a popular mulch. Wood chips are often spread around trees and landscaping to hold moisture. Grass clippings, leaves, and compost can be placed around garden vegetables, flowers, and in soil beds to keep down weeds.

Leaving blades of grass on the lawn is the most common mulching technique. All mulches help retain water in the soil. Mulch keeps the soil cool in the summer and warm in the winter. In fact, mulch is a form of drought insurance. Mulching is the easiest way to avoid generating organic waste in the first place. Leaving grass clippings on the lawn is the simplest type of mulching. But mulching is not practical for all residents and homes, and not all yard trimmings are easy to use as mulches.

Leaves
Leaves can also be mulched. Leaves left on the ground over the winter will not harm the grass, which goes dormant in most climates. In the North, winter puts leaves through a “freeze thaw” cycle that helps soften them for decomposition. Winter snow and Spring rains provide needed moisture for the subsequent breakdown. Layers should not be more than six inches thick.  Chopping, shredding, or mowing the leaves before using them as mulch can assist leaf mulching. 

Earthworms: The Mulching Assistant
Earthworms are the ultimate mulch specialists. The common nightcrawler, lumbricus terrestris, is a seasoned mulch hunter. Following every rain, or in the cool, moist mornings, hundreds of earthworms come to the surface to feed. These "mulch munchers" grab leaves, blades of grass, and other bits of organic matter and "tow" them back to their burrows. Deep under the soil, these worms store organic matter, excrete digestive juices to help them decompose the matter, and feast upon the resultant compost at a later date.

The worm devours the decomposed mulch and deposits the humus both in the burrow and on the surface as earthworm castings. Since the worms continually excavate and turn the soil, the humus layer remains near the root zone while the surface is continually cleared of debris. Earthworms will maintain a population level equal to the available feed or mulch. They keep the soil loose, aerated, and well drained. Working in harmony with other organisms, earthworms turn under the seasonal mulch layers, "vermicompost" it, and convert it to available plant nutrients.

Passive Composting
If yard trimmings are left to accumulate in a pile for extended periods of time, it is no longer a mulch and it begins to enter the realm of composting. The simplest compost piles are increasingly larger mounds of organic trimmings that are left to sit and rot over time. For some people, these "passive-compost" piles are largely a backyard disposal system. Even the most passive composter, the truly