Recycle Leaves, Needles & Trimmings

by Elmer Krehbiel, Master Gardener
December 10, 1999

The leaves and needles that fall from shrubs and trees are natures materials to retain soil fertility, conserve moisture, stabilize the soil temperature, and reduce weeds. If you have shrubs, trees or trimmings, now is the season to plan a recycling method to decay leaves, needles, and wood trimmings. Composting is any method to reduce the time to convert them to organic matter (humus). Some methods may require only several weeks, and others a year or more. Organic matter can be composted at home or hauled to the community composting facility.

The fallen leaves, needles, and wood trimmings should be recycled somewhere. Shredded wood is suitable material for the compost mix, and most wood chips are good for mulching.

Leaves are truly a valuable natural resource for providing organic matter and nutrients for the garden and/or landscape. Leaves contain 50 to 80 percent of the nutrients a shrub or tree extracts from the soil and air during the growing season. Pound for pound, the leaves from most shrubs and trees contain twice the mineral (N-P-K-etc.) content, usually no salts, and they have a lower pH than manure.

Therefore, leaves should be managed and used rather than bagged as trash. When they are bagged and set at the curb, many pounds of fertilizer elements leave your yard. It costs hauling fees and landfill space.

There are four ways in which leaves can be managed and used in the home garden and landscape:

Mowing

A light covering of leaves can be shredded by being mowed and left on the ground. This technique is most effective when a mulching mower is used or the area is re-mown with a regular machine without the bag attached.

Mulching

A lawn mower with a bagging attachment can be used to shred and collect the leaves. Shredded leaves will decompose faster than whole ones. They can be used as a mulch in vegetable gardens, flower beds, around shrubs, and around trees. They should be sprayed with water to prevent the wind from blowing them away. Apply a 3 to 6 inch layer around the base of trees and shrubs. In flower beds, a 2 to 3 inch mulch is ideal. For vegetable gardens, a thick layer of leaves, placed between the rows, functions as a mulch and all-weather walkway that will allow you to work in your garden during wet periods. Mulches are especially beneficial when used around newly established landscape plants, greatly increasing their likelihood of survival.

Mix into Soil

Leaves may be recycled by collecting and working them directly into the soils during the fall Apply additional nitrogen fertilizer.

A 6 to 8 inch layer of leaves tilled into a heavy clay soil will improve aeration, drainage, and fertility. The same amount tilled into a light, sandy soil will improve water and nutrient holding capacity.

Composting

No garden chore is easier or more pleasant than recycling dry autumn leaves. Composting is the biological reduction of organic waste to humus. Two parts leaves may be mixed with one part of grass clippings by volume, or leaves may be mixed with soil and nitrogen. Oak leaves are about 50 parts carbon to one part nitrogen. The ideal for composting is 25:1 up to 30:1. The process of composting can be carried out in piles, bins, trenches, bags or barrels.

The fiber content of leaves aids in improving the aeration and friability of soil structure. Oak leaves and pine needles are especially valuable to lower the pH level of the soil. An example of plants that need a slightly acid soil (pH of about 6.0) are: (vegetables) asparagus, beans, beets, broccoli, Brussels sprouts, cabbage, carrots, cauliflower, collards, sweet corn, cucumber, eggplant, garlic, kale, kohlrabi, lettuce, mustard, okra, onion, peas, peanuts, peppers, Irish potato, sweet potato, pumpkin, radish, spinach and squash; (fruits) apple, apricot, cantaloupe, grape, peach, pear, pecan, strawberry, tomato and watermelon; (lawn grasses) Bermuda, buffalo, rye and St. Augustine; (trees) ash, elm, and oak.

Plants requiring more acid soil (pH about 5.0) are: blackberry, blueberry, magnolia and pine. The pH information is available for several hundred species of vegetables, fruits, flowers, grasses, shrubs, and trees.

Dr. Elmer Krehbiel is the former President of Keep Brazos Beautiful. See his column in The Eagle.