Leave the Leaves

by Justin Wheeler

Leave the Leaves!

Thanksgiving and fall leaves – other than their Autumnal association, they seemingly have little in common. Yet, as a gardener and lover of the natural world, fall leaves are one of the things I am most thankful for this time of year. I thankfully rake them into my garden beds where I know they will add valuable organic matter to help me build beautiful soil from awful Pennsylvania clay. They will protect my plants over the winter, suppress weeds in the spring, and provide habitat for the bees and butterflies that capture nearly all of my attention in the spring and summer months. And best of all they do all of this for absolutely zero dollars, no delivery required!

Leaves and Lawn

According to a 2005 NASA estimate, there are around 40 million acres of lawn in the continental United States – making turf grass the single largest “crop” we grow. This disproportionate ratio of lawn to garden is the main reason we rake, mow, and blow. To mimic the natural ecosystem an animal needs, a layer of leaves needs to be at least a couple of inches thick.  While this would be too much of a good thing for turf grass to handle – research has shown that lawns actually benefit from a thin layer of leaves, and the rest can be piled up around ornamental trees, shrubs, and perennials to no ill effect.

If you must keep your landscape clear of leaves – try opting for using a rake or switching to battery powered or electric equipment. While electric and battery-operated equipment aren’t without their own environmental impacts, a 2011 test by automotive experts at Edmunds showed that a consumer-grade leaf blower emits more pollutants than a 6,200-pound Ford F-150 Raptor. This is because small gas-powered engines, such as those found in outdoor lawn and garden equipment, lack the emission reduction equipment found on larger engines. 

For the leaves you do end up raking to the curb, please be mindful to keep them curbside, on your sidewalk strip, rather than raking them onto the road or into the gutter. For the amount of time the leaves will be left on your lawn prior to collection, they will do no irreparable harm to the grass. Massive piles of leaves in the gutter, however, may impede the flow of rain into or clog and choke our already fragile storm water management system, contributing to flooding.

Better still would be to reduce your overall lawn footprint, replacing it instead with wildlife supporting plantings that can be future repositories for fall leaves.

Love birds, butterflies, and bees? Then leave the leaves!

While monarch migration is a well-known phenomenon, it’s not the norm when it comes to butterflies. In fact, the vast majority of butterflies and moths overwinter in the landscape as an egg, caterpillar, chrysalis, or adult. In all but the warmest climates, these butterflies use leaf litter for winter cover. Great spangled fritillary and wooly bear caterpillars tuck themselves into a pile of leaves for protection from cold weather and predators. Red-banded hairstreaks lay their eggs on fallen oak leaves, which become the first food of the caterpillars when they emerge. Luna moths and swallowtail butterflies disguise their cocoons and chrysalis as dried leaves, blending in with the “real” leaves. There are many such examples.

Beyond butterflies, bumble bees also rely on leaf litter for protection. At the end of summer, mated queen bumble bees burrow only an inch or two into the earth to hibernate for winter. An extra thick layer of leaves is welcome protection from the elements. There are so many animals that live in leaves: spiders, snails, worms, beetles, millipedes, mites, and more – that support the chipmunks, turtles, birds, and amphibians that rely on these insects for food.

It’s easy to see how important leaves really are to sustaining the natural web of life.

To shred or not to shred

Many organic gardeners opt for shredding their fall leaves for use in compost piles. While this is certainly a more environmentally friendly practice than bagging leaves and sending them to the landfill – shredded leaves will not provide the same cover as leaving them whole, and you may be destroying eggs, caterpillars, and chrysalis along with the leaves. We suggest that leaves in garden beds and lawn edges be left whole. Where space allows, consider creating a leaf pile and allowing it to break down naturally, or add the leaves gradually to your compost pile over time. Such efforts will keep critters safe and allow you to benefit from the rich garden gift that falls from the trees above.

It’s Free mulch!

In the past gardeners may have worried that fall leaves, matted down by snow or rain, would have a negative impact on their perennials. In reality, a thick layer of leaves provides additional insulation against cold weather, and can protect newly planted perennials when frost-heave may expose tender roots. Whole leaves have the same weed suppression and moisture retention properties as shredded wood mulch, and often last longer in the landscape. 

Regarding the potential for disease spread, most plant diseases that may be present on leaves at the end of the season, such as powdery mildew, will die off over the winter. When controlling for a particular leaf-borne fungal disease such as maple tar spot or apple scab, leaves should be removed from the landscape. If you are unsure, contact the Master Gardener Hotline or seek advice from a qualified arborist.

The bottom line

Simply put, when we treat leaves like trash – we’re tossing out a valuable resource. Leaves are a whose beneficial properties we pay to bring back in the form of mulch, compost, and chemical fertilizers. It’s time to re-think leaves, not as litter, but as a resource to be treasured.


Justin Wheeler is a Penn State Extension Master Gardener and formerly worked as Communications Specialist for the Xerces Society, a wildlife conservation organization dedicated to protecting invertebrates and their habitat. He can be contacted at:  studiowheeler@gmail com

 A version of this article originally appeared online at Xerces.org.