As leaves fall and the call to “leave the leaves” rises—from major news outlets to your next door neighbor—you may find yourself scratching your head as to how, exactly, to leave the leaves.

The slogan is a fun way to get people to consider a serious problem. We are in the sixth great extinction event in the history of the earth, which is directly affecting our food web. When one species goes extinct or its population declines severely, it can have a negative ripple effect on other species and the ecosystem as a whole. How does this tie into leaving the leaves in your own backyard? How does it help? And how do you do it?

Doug Tallamy can explain. He is an entomologist, a conservationist, and a professor in the Department of Entomology and Wildlife Ecology at the University of Delaware. He’s even written a book, Nature’s Best Hope, which is a blueprint for saving the earth one backyard at a time. (It’s on Gardenista contributor Melissa Ozawa’s list of favorite gardening books: see In Gratitude: How a Gift from a Boss Led to a Love for Gardening Books.) Below, Doug gives us the low-down on leaving the leaves.

Photography by Joy Yagid.

Q: Why do you think people don’t leave the leaves?

A: We do what we observed when we were kids. It’s been part of our culture to get rid of the leaves. You either burn them or you put them out in the curb for the city to take away, but you have to take them off your lawn and do something with them.

Q: What’s the easiest way to start?

A: Well, there is a conflict between having that perfect lawn and and the leaves that fall on the lawn. So people say “I gotta get the leaves off the lawn.” [The solution is to reduce] the area you have in lawn. The perfect way to start doing that is to create beds under the trees that you have. And you do that by raking the leaves into those beds. And in the beginning when you’re trying to actually smother the grass, [to make the beds] you rake a lot of leaves, you make it pretty thick. My son bought a house and the first fall, he called me up and said, “Dad, I got too many leaves. What should I do with them?’” I said: “Put them in your flower beds.” He said: “I don’t have enough flower beds.” I said: “Exactly.” You increase the amount of flower beds and that’s where the leaves go. The extra ones that just don’t fit in those flower beds can go into a compost heap.

Q: Does it matter what kind of leaves you have? What are the best leaves for this?

A: Oak leaves. [They] break down slower. So, that’s their main benefit. You never want to have bare ground. Maple leaves, tulip tree leaves, and birch—they all break down really quickly, so if that’s your leaf base, you’re going to have bare soil before the end of July and then your soil community really suffers. This is where oak leaves become important. One of the ecological benefits that leaves provide is to make a blanket on the ground that keeps the humidity and moisture in the soil because everything that lives in the soil requires high moisture levels. This includes the mycorrhizae and all of the creatures that are breaking down those leaves. They all require high humidity. It’s funny that people rake up the leaves, and they go out and they buy bark mulch…

The other major thing that leaves are doing is transferring the nutrients that your tree used that year into the soil so that they get to use it again. If you rake those leaves away, you’re slowly starving your trees and all the rest of your plants because you keep throwing away the nutrients. Most people don’t fertilize their trees and it’s hard to do it properly. It’s easy to over-fertilize them. So the very best thing is to keep all the leaves that fall on your property, and they should be as close to the trees as possible so that they can break down and provide the nutrients that that tree needs.

Q: How does one deal with an HOA or municipal regulations about lawns?

A: Well, the lawn you keep is going to be mowed. It’s going to be manicured. That’s the way you edge those new beds you’ve created. So it looks nice and neat. [In the leaf beds around the trees that you’ve created], the perfect mulch is green mulch. So you actually want to plant through the fallen leaves. You want ground covers like ferns and May apples, wild ginger, and goldenseal—all kinds of spring ephemerals. That’s what should be under your trees. The leaves are nestled in there. Then it becomes a beautiful garden. But you’ve still got that mowed strip of grass surrounding that, and it’s neat and your HOA says, okay, you are taking care of your property. That’s all they care about. There’s no conflict.

How to “Leave the Leaves”

1. To reduce your lawn, rake a thick layer of leaves onto areas where you want to smother grass and create a new bed for natives instead (e.g., around a tree).
2. To help your already existing garden beds, move leaves off your lawn and onto the beds. They will act as both mulch and, as they break down, compost.
3. To help your lawn, mow fallen leaves (a few times to chop them into small bits) and rake them back onto the lawn.

See also:

• Your First Garden: What You Need to Know About Raking Leaves
• The Rake vs the Leaf Blower: Which Is Better?
• Gardening 101: What to Do in the Winter for Healthier Soil in the Spring

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