A crisp wind rattles the trees, and with it comes the yearly cascade of gold, orange, and brown leaves piling up in our yards. For many of us, fall clean-up is as familiar as carving pumpkins or stacking firewood: pull out the rake, bag the leaves, and set them out for disposal. But have you ever wondered where those leaves go once they leave the curb–or what happens when they get left on the lawn?
In forests, fallen leaves play a quiet but essential role. They break down slowly through winter and spring, releasing nutrients that feed the soil and protect the roots of trees and understory plants. They create pockets of shelter where insects and amphibians can survive the cold months, waiting for warmer days to emerge. Birds depend on this hidden world too, returning in spring to feast on the insects that developed in last year’s leaf litter.
Fallen leaves on lawns have a similar effect. When you leave the leaves in place, you’re mimicking the natural process that has kept forests healthy for thousands of years. Leaves settle into the grass and are broken down by microorganisms, adding organic matter that enriches the soil and helps it retain moisture. Over time, this improves the health of your lawn and reduces the need for fertilizer. Around shrubs, perennials, or in vegetable beds, leaves act as a natural mulch, insulating plant roots against winter cold while slowly breaking down into nutrient-rich soil that supports next year’s growth. Removing leaves from our yards interrupts this cycle, leaving fewer nutrients returning to the soil.
Beyond the soil, fallen leaves are also critical for wildlife. Fireflies, for example, spend most of their lives in the larval stage living under leaf litter, feeding on slugs and snails until they emerge in summer to light up our evenings. Luna moths and mourning cloak butterflies overwinter as chrysalises or adults tucked safely into leaf piles. Bumblebee queens burrow beneath the insulating layer of leaves to survive until spring. By clearing away the leaves, we sweep away the very places these species rely on to make it through the cold months.
Of course, not every leaf can stay put. A thick layer can smother grass if left all winter, and leaves piled on sidewalks or pavement are easily washed into storm drains. In water, leaves decompose much faster than they do on land. This sudden release of nutrients from leaves–especially nitrogen and phosphorus–acts like fertilizer for algae, clouding the water, depleting oxygen levels, and stressing fish, invertebrates, and other aquatic life. In fact, fall leaf litter is now recognized as one of the biggest seasonal contributors of phosphorus pollution in urban and suburban watersheds.
Fortunately, there are simple ways to keep the benefits of leaves without sending their nutrients downstream. Mulching them directly into a lawn is one of the easiest solutions: a mower chops leaves into fine pieces that settle into the grass and slowly return their nutrients to the soil. You can also gather leaves into backyard compost piles to create rich soil for spring gardening. Another option is to use them as natural mulch around perennials, shrubs, or in a quiet corner of the yard where insects and small animals can find shelter. Even these small patches create valuable habitat and insulation through the coldest months.
This fall, when you head outside with a rake in hand, take a moment to consider where those leaves will go. A leaf-covered lawn means more food and shelter for pollinators, healthier soil for next year’s garden, and cleaner water in the lakes and rivers we all depend on. By leaving the leaves where they can do the most good, we take part in the same seasonal cycle that has nourished New England’s landscapes for thousands of years.