By Fern Campbell
Piedmont Master Gardener
Fallen leaves are a gift from Mother Nature to our yards and gardens. In addition to providing many other benefits, such as creating shade, sequestering carbon, filtering air pollution, and giving food and shelter to wildlife, trees drop leaves that are an organic powerhouse—nature’s key ingredient in building soil.
When leaves drop and decay on our yards, they add nutrition and organic matter. Think of them as a slow-release fertilizer that can be used as mulch with just a little bit of processing, transforming them into a great amendment for even the poorest of soils. And all for free.
Every fall, households with trees need to do something with leaves that cover their yards. Sometimes all it takes is a couple of passes with the lawnmower to mulch them into the lawn, but too often folks move them to the curb for pickup, bag them up to be hauled away to the dump, or burn them.
Autumn leaves don’t have to become trash. On the contrary, the combination of fallen leaves and grass clippings makes the perfect recipe for homemade compost and the greatest amendment for our clay soil. In fact, leaves are such a valuable resource that many of us gardeners have been known to gather leaves from others’ curbs. Please keep this organic matter out of the landfill, where it can produce methane gas as it breaks down.
And please don’t burn leaves. Leaf burning wastes an organic resource while releasing toxic irritants, various carbons and particulate matter into our atmosphere, which can increase air pollution and cause respiratory illnesses. It also presents a fire hazard.
Let’s take a look at what leaves do for us and at environmentally sound ways to manage your leaves if you have an overabundance.
Lawns actually benefit from a thin layer of leaves. Mow with blade height at about three inches and pass over until you can see green grass underfoot, so that the layer is not so thick as to smother the grass. Over time, the leaf mulch returns nitrogen to the lawn and adds organic matter to the soil. For tips on how to mulch leaves into the lawn, view this video produced by Michigan State University Extension.
Leaves can stay where they fall in many places, including wooded areas, perennial flower beds and over tree roots. Fall leaves protect plants against freezing winter weather and make a great mulch, but do shake leaves off shrubs and permanent plants so as to not weight them down.
Shredded leaves are an excellent addition to the soil for the established vegetable garden as well as for the preparation of new gardens. A lawnmower with a bag attachment will do the job. When used as a mulch surrounding your vegetables, shredded leaves help conserve water, suppress weed growth and prevent soil erosion. Leaves are a superior alternative to wood chips and are certainly cost effective and nutrient filled.
Compost piles work more efficiently when you mix the correct combination of green (fresh) materials, such as grass clippings, and brown (dried) materials, such as autumn leaves. By incorporating autumn leaves, you will help decomposition, resulting in a better end product. Detailed information on how to compost yard waste and use it in your landscape is available from Virginia Cooperative Extension.
Layering leaves in your garden provides habitat and winter protection for wildlife, including valuable insects. “Leaf litter”— those layers of decomposing leaves—serve as cover and foraging areas for many creatures. Toads, box turtles, salamanders and shrews, for example, live in leaf layers or rely on them for food. Many birds flip leaves in search of insects to feed their young. Leaf cover improves their odds of finding protein-rich invertebrates such as beetles and earthworms.
The vast majority of butterflies and moths overwinter in the landscape as an egg, caterpillar, chrysalis or adult. Luna moths and swallowtail butterflies disguise their chrysalises and cocoons as dried leaves, blending in with the real leaves. Bumble bees also rely on leaf litter for protection. With just these few examples, it is easy to see how important leaves are to sustaining the natural web of life.
A note of caution: shredded leaves do not provide the cover that whole leaves do, and shredding can destroy eggs, caterpillars and chrysalises. For that reason, the Xerces Society—an organization committed to protecting pollinators—recommends leaving the leaves whole in garden beds for the good of these creatures.
Skip the Fall Cleanup
Leaves are often an overlooked resource, so think twice before you carry them to the curb or stuff them into bags. And depending on where they fall, they may not need to be raked, mowed or shredded—in the fall or even the next spring. You work hard all summer to tend to your gardens without using pesticides, and to provide flowers, food and a place to nest for pollinators, insects, birds and other critters. When we send leaves out in the trash, we are tossing out some of the beautiful moths and butterflies that we worked so hard to attract, and we are eliminating a place where birds look for food.
Scientists tell us that many bird and insect species are on the decline. Indeed, a 2019 study published in the journal Science shows that the abundance of birds in North America has dropped 29 percent just since 1970, amounting to nearly 3 billion fewer birds. We can help protect birds and pollinators by taking simple actions in our lives and in our yards—like leaving the leaves. We have the power to do things differently, for the good of wildlife and our shared environment.
Online Resources on Healthy Habitats
Explore more ways to provide and protect habitat for wildlife in your yard. Visit Xerces.org to learn about where invertebrates overwinter (hollow stems, tree branches and brush, soil), how to provide winter cover (brush piles, rock walls, other nesting options), and the timing of any spring cleanup.
Read about more ways to create an inviting habitat for pollinators and other wildlife. In addition, use the search feature on the Piedmont Master Gardener website to find numerous articles on attracting pollinators to your landscape.
