How and why you should leave the leaves in your yard this fall

CLEVELAND, Ohio — Dealing with leaves is an annual fall tradition for Northeast Ohioans.

The leaves often end up in paper bags or piles on the tree lawn, destined for a community composting facility, or worse, in plastic bags that end up in a landfill. Why not try something different this year and keep this precious resource for yourself?

The trees on your landscape invested nutrients and energy throughout the spring and summer to produce and maintain those leaves. You can return much of that investment and benefit local wildlife by keeping the leaves in your yard.

Consider mulching your lawn leaves in place them rather than raking or blowing them. All you need to do is set your mower to mulch and use a high setting (3 1/2-4 inches) to accommodate the leaves. However, as you approach the end of the season, you should gradually lower your mower to around 2 inches. This will help prevent snow mold from developing over the winter. Don’t forget to raise your mower back up in the spring!

If you have lots of leaves, it may take more than one pass to chop them all up with the mower. You may also need to spread them out a bit if they mostly fall in one area. The mulched leaf pieces will eventually work their way down to the soil surface where they will be broken down by worms, fungi, and other decomposers to benefit your lawn and your trees. Studies suggest that mulched leaves also help prevent weed seeds from germinating in your lawn.

If you have too many leaves to mulch with a mower, use them elsewhere in your landscape rather than having them hauled away. Transporting leaves is costly to our communities and our environment. Keeping your leaves saves money, decreases air and noise pollution, and releases fewer greenhouse gases into the atmosphere. It also benefits your landscape and local wildlife.

Spreading leaves around the bases of large trees in your yard is an excellent way to use them. However, be sure to avoid piling them around the base. Spread leaves at an even thickness, leaving a small gap (several inches) between the trunk and the leaves. Aim to create a “leaf donut” rather than a “leaf volcano.” The leaves will compact with time, so the layer can be quite thick: up to 6” for shredded leaves and thicker for whole ones. If you have the space, the ring can be quite large in diameter. This is a great way to reduce the size of your lawn!

Spreading leaves around the base of a tree is good not only for trees, but also for insects and other wildlife. Leaves provide habitat for small animals to overwinter and to complete their lifecycles. “Soft landings” of leaves, sticks, and other natural debris under trees support insect larvae when they drop to the ground after spending the summer feeding in the treetops. To learn more, search “soft landings insects” on the internet.

Maybe you prefer a more manicured look for your landscape? Find a place in your yard where you can deposit the leaves inconspicuously. Using them around the bases of shrubs can be a great option, especially if you have a shrub border along the edge of your property. Borders are places where unwanted volunteer trees and non-native invasive plants frequently sprout up. A thick layer of leaves will help suppress invasives and other weeds while blending into the landscape. They will hardly be noticed.

If you don’t want to rake leaves, use your leaf blower as a leaf vacuum to suck them up and shred them (many blowers can be used as both). An advantage of shredding leaves is that they break down more quickly than whole leaves and won’t blow away as easily. A disadvantage is that shredding can kill insects (such as moths and fireflies) that may be hiding in the leaf litter.

Leaf humus – decomposed leaves – is an excellent soil amendment, especially for vegetable gardens. You can make your own leaf humus by piling your leaves in a corner of your yard and letting nature run its course. However, it can take two to three years to produce quality humus. You can speed up the process by purchasing or making a composting bin. There are many options for materials and styles, but a good size is 3-4 inches in all dimensions. If you shred your leaves and periodically turn the pile, leaf humus can be ready in six to 12 months. You can do it even more quickly by mixing in fresh vegetation – but composting with “browns” and “greens” is a topic for another column!

Darin Croft is Professor of Anatomy at Case Western Reserve University and has been a Master Gardener Volunteer since 2008. He is a Research Associate at the Cleveland Museum of Natural History, and he also volunteers for Nature in my Backyard, a program that helps Cleveland-area homeowners build local biodiversity.