The beloved maples, oaks, ash and other deciduous trees of our region are not only a beautiful part of our natural and garden environments, but they are also profoundly efficient organisms continually helping to make our Earth a healthier place. Throughout the growing season, tree leaves work on a variety of critical fronts: they help provide nutrition for the tree itself, filter contaminants from the air, produce life- sustaining oxygen, cool the air and earth beneath, and soften the impact of heavy rainfall. Leaves also serve as food for a variety of insects and caterpillars that will become important pollinators – or a critical food source for birds and other wildlife.
As the growing season comes to an end and leaves fall, they persist in playing a key role in the lifecycle that sustains our ecosystem. Leaf litter is the natural winter habitat for many of our most important insects. The Xerces Society for Invertebrate Conservation, an international nonprofit organization that protects the natural world through the conservation of invertebrates and their habitats that in addition to avoiding pesticides and adding the right plants to our landscapes, “…one of the next most valuable things you can do to support pollinators and other invertebrates is to provide them with the winter cover they need in the form of fall leaves…the vast majority of butterflies and moths overwinter in the landscape as an egg, caterpillar, chrysalis, or adult. In all but the warmest climates, [they] use leaf litter for winter cover.”
When leaves are allowed to remain on the ground to decompose, they return nitrogen, phosphorous, potassium, and twelve additional micronutrients and organic particles to the soil. These essential elements feed the roots of plants above the ground as well as the diverse and vital community of “good” bacteria, fungi, protozoa and nematodes, mites, springtails, earthworms, and other tiny beneficial organisms beneath the surface. And as leaf litter decomposes, it aids carbon sequestration, a natural process by which carbon dioxide is removed from the atmosphere and converted to biomass.
While the colorful autumn spectacle is just beginning, our London Plane trees have already dropped most of their leaves and Greenwood’s facilities and horticulture staffs have already started “harvesting” our annual bumper crop. While many will remain on the ground in our wooded areas, a substantial portion will be chopped by lawnmowers and spread as a nutrient rich, weed suppressing, moisture retaining mulch on cultivated areas throughout the gardens. The remainder will be gathered and moved to composting areas of Greenwood Gardens.