AMES, Iowa – At this time of year homeowners clearly understand why another term for “autumn” is “fall.” With the slightest breeze, shade and ornamental trees send a shower of leaves to carpet the lawn, drive and sidewalk. Horticulturists with Iowa State University Extension and Outreach answer homeowners’ questions as they decide how to deal with fallen leaves. To have additional questions answered, contact Hortline at firstname.lastname@example.org or call 515-294-3801.
Turfgrass plants use sunlight, water and nutrients to manufacture food. In fall, lawn areas beneath large trees are often completely covered with leaves. The leaf debris prevents the turfgrass plants from manufacturing and storing food prior to winter. A thick layer of leaves (little or no grass is visible) will need to be raked up and removed. It’s possible to deal with a thin layer of leaves (areas of grass are clearly visible) by chopping them up with a mulching mower. Small quantities of shredded leaves will filter down into the grass canopy rather than rest on the grass surface.
Leaves contain high levels of carbon and small amounts of nitrogen. The microbes that decompose leaves and other types of organic matter require nitrogen for their own metabolism and growth. A compost pile composed mainly of leaves decomposes slowly because the leaves don’t contain adequate levels of nitrogen for the microbes.
To promote decomposition, mix leaves with grass clippings or other materials high in nitrogen. If possible, shred the leaves prior to composting. The smaller the size of the material, the faster it will decompose.
Construct the compost pile in layers. Each 6- to 8-inch-layer of plant material should be topped with 1 inch of soil or compost. A small amount of an all-purpose garden fertilizer, such as 10-10-10, can also be added to supply nitrogen to the microbes. Continue to build the compost pile in layers until it is 3 to 5 feet high.
Finally, water the pile regularly and turn it about once every two weeks.
Shredded or composted leaves are an excellent mulch for vegetable gardens, raspberry plantings, perennial flower beds and around trees and shrubs. While the leaves of some trees, such as oak, are acidic, they can be safely used in the yard and garden. An oak leaf mulch has little effect on soil pH.
Leaves are a poor winter mulch for strawberries and herbaceous perennials. Plants covered by leaves over the winter months may be damaged due to excess moisture trapped under the leaves. Clean, weed-free wheat, oat or soybean straw is an excellent winter mulch for strawberries and perennials.