A reader said he had heard of the practice of shredding leaves prior to using them as mulch but wondered about the reason behind it. Was it just to make it easier to dispose of the leaves, since, once shredded, the load would be more compact? Or was there some other benefit?
The tree leaves that accumulate in and around your landscape represent a valuable natural resource that can be used to provide a good source of organic matter and nutrients for use in your landscape. It is an established fact that the trees in one acre of forest shed as much as two tons of leaves each fall. You may complain, as you lean wearily on a leaf rake, that your neighborhood outdoes any forest, but be thankful. Hang on to your leaves. And if your neighbors don’t want them, hang on to theirs. It makes no sense to send valuable treasure to the dump.
In forests, pastures and other natural settings, tree leaves and other organic wastes form a natural carpet over the soil surface which conserves moisture, modifies temperatures and prevents soil erosion and crusting. In time bacteria, fungi and other natural occurring organisms decompose or compost the leaves and other organic material, supplying the existing plants with a natural, slow release form of nutrients. You can, and should, take advantage of this same concept.
Leaves are truly a valuable natural resource! They contain 50 to 80 percent of the nutrients a plant extracts from the soil and air during the season. Therefore, leaves should be managed and used rather than bagged and placed at curbside to be picked up and hauled to landfills. There are four basic ways in which leaves can be managed and used in the landscape.
Leaf Management – Mowing
A light covering of leaves can be mowed, simply leaving the shredded leaves in place on the lawn. This technique is most effective when a mulching mower is used. In fact, during times of light leaf drop or if there are only a few small trees in your landscape, this technique is probably the most efficient and easiest way to manage leaf accumulation.
Leaf Management – Mulching
Mulching is a simple and effective way to recycle leaves and improve your landscape. Mulches reduce evaporation from the soil surface, inhibit weed growth, moderates soil temperatures, keep soils from eroding and crusting, and prevent soil compaction. As organic mulches decompose, they release valuable nutrients for use by your landscape plants.
Leaves can be used as a mulch in vegetable gardens, flower beds and around shrubs and trees. As an option to raking, a lawn mower with a bagging attachment provides a fast and easy way to shred and collect the leaves. Leaves that have been mowed or run through some other type of shredder will decompose faster and are much more likely to remain in place than unshredded leaves.
Apply a 3 to 6 inch layer of shredded leaves around the base of trees and shrubs. In annual and perennial flower beds, a 2 to 3 inch mulch of shredded leaves is ideal. For vegetable gardens, a thick layer of leaves placed between the rows function as a mulch and an 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 the likelihood of their survival.
Leaf Management – Soil Improvement
Leaves may be collected and worked directly into garden and flower bed soils. A 6 to 8 inch layer of leaves tilled into a heavy, clay soil will improve aeration and drainage. The same amount tilled into a light, sandy soil, will improve water and nutrient holding capacity.
A recommended strategy for using leaves to improve soil in vegetable gardens and annual planting beds is to collect and work them into the soil during the fall. This allows sufficient time for the leaves to decompose prior to spring planting. Adding a little fertilizer to the soil after working in the leaves will hasten their decomposition.
Leaf Management – Composting
Knowledge of composting dates back to the early Greeks and Romans. The Arabs kept the science of composting alive during the Dark Ages, and it continued throughout the Renaissance. From Shakespeare’s Hamlet comes the line “spread the compost on the weeds, to make them ranker!” In America, the value of composting was recognized by George Washington, Thomas Jefferson and George Washington Carver. Today, knowledge and interest in the science of composting is increasing dramatically. Whether an ancient art or a modern science, composting is a useful and environmentally sound gardening practice for you.