Why You Don’t Need to Rake Leaves

You might want to kick it or step on it to hear the satisfying crunch underfoot. You might even be tempted to jump into it.

But that pile of leaves is home to an entire ecosystem filled with critical organic matter. In fact, those leaves probably shouldn’t be piled at all.

In recent years, some naturalists have called for an approach known as “leaving leaves” when they fall to the ground, which would return organic materials back to the soil.

“A forest has the richest soil there is, and that happens because leaves are falling off the trees and decomposing right there and organic materials are going back into the soil,” said Susan Barton, a professor and extension specialist in landscape horticulture at the University of Delaware. “We should be doing that in all of our landscapes, but we’re not.”

However, because of local ordinances, homeowners’ associations and personal preferences, that option is not always realistic. But that doesn’t mean you shouldn’t try, naturalists say.

What lies beneath?

When leaves fall from a tree, the plant material covers the tree’s root zone and begins to break down, returning nutrients to the soil. Think of it as organic mulch or fertilizer, said David Mizejewski, a naturalist with the National Wildlife Federation, which has designated October as Leave the Leaves Month.

Within that fallen leaf layer is an entire ecosystem, Mr. Mizejewski said, home to all sorts of animals, including invertebrates, reptiles, amphibians and pollinators. Many species of moths and butterflies, for instance, rely on the leaf layer to complete their life cycle, Mr. Mizejewski said, as more than 90 percent of moth species attach themselves to leaves and spend the winter in cocoons buried among the foliage. Those moths and butterflies, in turn, are a critical food supply for many birds.

Leaf litter, as it’s sometimes known, can also be a habitat for ticks. So if you’re dealing with a large pile of leaves, be sure to cover yourself fully.

“When we are overly zealous about getting rid of every single leaf in our neighborhoods, we literally wipe out entire populations of these pollinators,” Mr. Mizejewski said. “These are species that can live right alongside us if we just give them some habitat.”

Think about it as a good, better, best approach.

The most “natural” way to create that circular ecosystem is to leave it alone, Mr. Mizejewski said. But that option is probably not realistic for most homeowners facing restrictions.

The next best option, Mr. Mizejewski said, is to mulch in place by mowing over a light layer of leaves and returning the foliage to the soil. If that’s not an option, you can rake leaves directly into garden beds and scatter them around the roots and stems of plants, about three to five inches deep. You can also rake them into a compost pile and let them decompose over the course of the year. The leaf mulch can then be applied to lawns or garden beds.

Some towns, like Maplewood, N.J., where Mr. Mizejewski lives, have a municipal leaf composting program that recycles the leaves for residents and turns them into compost.

“The most important thing to do is to try and keep them on your property,” Mr. Mizejewski said.

Leaving leaves is not a one-size-fits-all solution.

While some groups, such as the National Wildlife Federation, consider lawns to be what Mr. Mizejewski described as a wildlife “wasteland,” Dr. Barton said that leaving a thick layer of leaves could block light and stunt grass growth.

Whatever you do, do not dump leaves near a gutter or put leaves in trash bags.

“The very worst thing is to send them to a landfill where they won’t get used as the resource that they are,” Dr. Barton said. “It’s recycling something that already exists on the property and it makes a much better soil structure.”