Leaves, Leaves - Everywhere!

This article was originally published on October 18, 2006 and expired on November 15, 2006. It is provided here for archival purposes and may contain dated information.

As the 'ole saying goes, "What goes up, must come down" – and leaves are no exception. With the advent of the cooler autumn temperatures, many trees begin to display a magnificent display of color. However, even the prettiest colored leaves will eventually fall to the ground, although some trees, such as the oaks, will wait until late winter for leaf drop to occur. But leaf disposal should not present a serious problem for the homeowner, reports Bob Frazee, University of Illinois Natural Resources Educator, because there are a variety of uses for them.

How many leaves might a typical homeowner have to rake this fall? Well, Frazee reports that an ordinary, mature tree may have as many as a quarter of a million leaves on its branches. So, if you live on a one-half acre lot and have 10 mature trees.....well, try not to think about it!

Leaves make an excellent mulch beneath trees, shrubs and other landscape plantings. As compared to fresh green grass clippings, Frazee suggests that tree leaves that drop in the fall are relatively dry and can be used as mulch with little or no odor problems. Leaves collected in the fall with a lawn mower bagger will contain some grass clippings. Frazee reports that this mixture of leaves and grass can also be used as a mulch without odor problems.

Leaves are also an excellent source material for compost. The microorganisms found on leaves are sufficient to start the composting process. When placed in a compost pile in the presence of adequate moisture, leaves will decompose into an excellent organic soil amendment that can be used as a soil conditioner.

According to research studies, leaves from different tree species will decompose at different rates, but the product is the same. Leathery leaves such as oak leaves contain more lignin and other woody substances and therefore take longer to decompose than fine-textured leaves. Leaf decomposition can be accelerated by increasing the surface area by mowing the leaves while they are being collected or shredding them after collection.

Another tip from Frazee is that leaves collected in a lawn mower bag will contain some grass clippings. Since they contain more nitrogen than the leaves, they will help to increase the rate of decomposition. Additional nitrogen will also speed the rate of composting.

Dry leaves will require moisture for composting. In early autumn, leaves will have a moisture content of 30-40%. Late season leaves will have less than 20% moisture. Leaf composting proceeds best with 40-60% moisture. It is a good idea to use a garden hose to wet leaves that are to be composted. Since fresh grass clippings contain 60-70% moisture, they can be mixed with leaves to provide moisture. If the compost pile begins to smell, it is an indication that it is too wet.

Oxygen is needed for aerobic decomposition to occur. Frazee cautions that if the oxygen supply is too low, anaerobic decomposition will occur and the compost pile will begin to smell. This problem can be corrected by turning the pile to add more air.

As leaves decay, they produce heat. The heat of an active compost pile will peak at 140 – 150 degrees Fahrenheit (F). When the temperature of the compost pile begins to decrease it is time to turn the pile. Ideally, the turning process should be repeated three to four times to get finished compost. Once the leaves turn into leaf compost, Frazee recommends that it be used as a soil conditioner to improve the tilth and fertility level of soils in the yard and garden.

Pull date: November 15, 2006