Climate change, habitat loss and pesticides are causing dramatic declines in populations of insects and the birds who need them—with likely dire consequences for humans’ quality of life and even our survival. Yet while urban gardens and parks are increasingly seen as important places to sustain biodiversity, a curious autumn ritual continues: “cleaning” our yards in preparation for winter. Sadly, this outdated habit of removing organic material (especially leaves) actually harms the ecological health of our yards and our environment.
Insects rely on fallen leaves and other natural debris to cover and insulate them from the elements during winter, and removing all this valuable organic material removes them too. Fallen leaves are not litter, but are food and shelter for butterflies, moths, and many other beneficial insects who keep our ecosystem working. Bugs, however annoying or creepy to some people, are not optional. Without insects and the “services” that insects provide, such as pollination, the food chain we rely on would collapse, including in our own vegetable gardens.
The Xerces Society, a science-based international nonprofit working to protect the natural world by conserving invertebrates and their habitats, advises: “Abandon the brush. Let the logs be. Surrender the soil. Disregard the garden. The colder seasons call for a healthy amount of neglect in the outdoors to ensure invertebrates have shelter and food.”
And when they say leave the leaves, they also mean save the stems of garden plants. Most insects spend winter hidden in leaves, hollow stems, trees, brush piles and soil. Dead stems, such as last year’s last year’s raspberry or wildflower stems, provide nesting space and shelter for many types of beneficial insects. In the fall, leave dead stems intact; in the spring, cut back the dead stems, leaving the stubble at heights from 8 to 24 inches. “Insects will make their nests inside and larvae will develop over spring and summer. These insects hibernate in the stems over fall and winter until they emerge as adults the next spring.”
Doug Tallamy, entomologist, researcher and University of Delaware professor, also advocates for a new approach to conservation that starts in our yards. The choices we make about how we clean up in fall and spring can help counteract an overdeveloped, fragmented landscape that threatens the food web. He explains that caterpillars are the major group of animals that transfer energy to birds and other animals. A lot of caterpillar cocoons are rolled up in the leaves of trees. So when we rake those leaves and burn them or bag them as trash, we’re throwing away most of the life created in our yards.
Tallamy encourages us to think of leaves the same way we think of water: the best practice is to keep both on your property. “Don’t let water run off. Same thing with leaves. So all the leaves that fall on your property should stay there, because that’s part of the cycle. They’re going to return the nutrients to the soil that were taken up by the trees’ roots and used all summer long, so the tree gets to use them again. Leaves are the perfect mulch.” Why rake up your leaves, throw them away and then go buy bark mulch in the spring?
As the Xerces Society explains, "Leaving the leaves and other plant debris doesn’t have to mean sacrificing your yard to the wilderness. The leaves don’t need to be left exactly where they fall. You can rake them into garden beds, around tree bases, or into other designated areas. Too many leaves can kill grass, but in soil they can suppress weeds, retain moisture, and boost nutrition.”
At least: think twice before you rake, mow, and blow this year; at best: don’t do it! Save your garden clean up until the spring. Wait until spring temperatures are in the 50s for at least a week. By then, insects living there will emerge and start their cycle of life again.
Put Down Those Pruners by the Xerces Society
Bee-Friendly Garden Cleanup by Heather Holm
Six reasons to NOT clean up the garden this fall by Jessica Walliser
Constance Pepin is co-founder of the Friends of Roberts Bird Sanctuary and co-leader of the Linden Hills Trolley Path Naturescape project.
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