Before the last of this fall's leaves were gone completely, the season's first snowfall dusted some of the higher elevations in the St. John Valley Monday morning. Credit: Julia Bayly | BDN

Fall is here, and a layer of colorful leaves will soon blanket lawns across the state of Maine. Tidying up the leaves on your lawn before winter will make spring clean-up much easier for homeowners. Some wildlife specialists, however, think you should leave the leaves over the winter to promote the health of your local ecosystem.

“Our typical lawns have little to no ecological value, and instead often serve as potential hosts for exotic or invasive species of plants and insects,” said Eric Topper, education director at Maine Audubon. “Leaving leaves is good for conserving species and the critical role they play within the larger ecosystems.”

Lawns covered with leaves can serve as habitat and other roles in the ecosystem of your yard, experts say.

The benefit of fallen leaves to wildlife

Many species make habitats in the autumnal leaf layer. Salamanders, frogs and toads rely on the protection and food provided by leaf litter during the winter. Squirrels and chipmunks use leaf material to help build their dens. Earthworms break down fallen leaves for sustenance. Insects will nest in fall leaves, and then go on to feed other animals up the food chain.

“Countless bird species and many mammals forage for insects and seeds amongst leaf litter, especially in fall and early spring when it isn’t covered by snow and ice,” Topper said.

Topper added that a number of caterpillars of butterfly and moth species pupate, or form cocoons and chrysalises, under cover of the leaves during the winter.

“The moths and butterflies will emerge in spring to look for mates and some will pollinate native plants and crops for people,” Topper said.

The benefit of fallen leaves to your lawn

Leaving falling leaves can also be good for your lawn. Fallen leaves protect the soil by insulating the ground and keeping soil from drying out or freezing too quickly. A leaf layer can help limit invasive seeds finding exposed soil in which to germinate and spread. Leaf litter also makes an excellent natural mulch that will help suppress weeds while simultaneously fertilizing the soil as they decompose.

“The leaves have nutrients that leach into the soil, and tiny insects, fungi, and other organisms also help break down and digest the material leaving rich organic waste behind, which in turn helps feed the roots of plants growing nearby,” Topper said. “Some fallen leaves provide specific nutrients that benefit other plants. For example, pine needles help contribute to soil acidity which benefits many evergreens, azaleas [and] roses.”

An added bonus: leaf litter doesn’t cost anything.

“[The lawn care industry] is a multibillion dollar industry,” said Sarah Kern, community engagement specialist at the Center for Wildlife. “Why would you spend money on mulch and fertilizer when you can just make your own?

Leaving a layer of leaves can even help your lawn look even better come spring.

“Once the temperatures freeze and grasses go dormant for the winter, lawns don’t use or need sunlight until spring,” Topper said. “Getting buried by a thin layer of leaves will only help. Most of us have experienced raking up leaves in early spring to find uniquely lush, green, healthy grass underneath. This grass has enjoyed the protection and nutrients described above, while the exposed sections of lawn have essentially shut down to protect itself.”

Small changes you can make in lawn care for the environment

The density of your leaf layer matters. While a thin layer is good, a thick layer of fallen leaves may smother your lawn. Kern said to make sure leaves are evenly distributed and not densely piled into one location to prevent patches of dead lawn come spring.

In future years, Kern said that homeowners with heavy leaf cover should try other approaches. For example, homeowners can turn fallen leaves into mulch by choosing a lawnmower that has a mulching attachment to help prevent matting. Kern said that doing so will not give as many habitat benefits as leaving the leaves as they fall, but it is better than removing them entirely.

“By mowing over the leaves to turn them into smaller pieces, you’re going to enhance the lawn’s fertility,” Kern said. “I believe that on the spectrum of it all, if you were going to be breaking up the leaves with a lawnmower and things like that it’s much better than having ChemLawn [now known as TruGreen] come in.”

What to do if leaving leaves isn’t an option

If you must have a tidy look in your yard — for example, if you are part of a homeowners’ association — you can rake leaves off your lawn (avoid leaf blowers — they cause noise and air pollution) and use them for compost or as mulch in your planting beds.

“You’re enabling places for critters to hide and forage, [which] also helps protect and fertilize the plants. This precious organic material is more treasure than trash,” Kern said.

Some municipal recycling centers may accept leaf litter for compost. Local farmers or gardeners may also be interested in leaf litter for their own planting plots. Whatever you do, just avoid throwing fallen leaves in the trash.

“That has a lot of issues,” Kern said. “You don’t know what you’re raking up in those leaves, then where are the leaves going? [Plus,] it would take more effort.”

Kern emphasized that not raking up your leaves doesn’t have to be an absolute for your whole lawn. You can start experimenting with it and see if it suits you.

“If you have this big beautiful lawn that you love, but maybe you have a section that you experiment with and not pick the leaves up,” Kern said. “It’s more about patience and dedication. It can be overwhelming to try and make ethical decisions about what you’re doing to your property, with your life, what you’re driving, wearing, eating — all those things. We have to remind ourselves to be gentle [and] patient with people and meet them where they’re at.”

Correction: An earlier version of this story failed to fully identify Sarah Kern.

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