By Paul Prill

A recent survey by the National Wildlife Foundation discovered that 90 percent of participants favored leaving their fall leaves to help the environment and wildlife. Yet only 15 percent actually left their leaves on their properties. 23 percent threw away between 6 and 10 bags of leaves, and 11 percent threw away more than 10 bags. What about the remaining 51 percent? Living under the requirements of HOAs demanding that they bag and removed leaf litter (We need to work on easing this restriction). The fact that we call it leaf litter betrays a poor understanding of how nature works to renew itself.

It’s not as I have suggested in the past that the leaves release important nutrients to the soil. The actual nutrient content of dead leaves is minuscule (about 1 percent nitrogen, and less that 0.1 percent each of phosphorus or potassium according to a 2022 Iowa State University Extension analysis). But what the study overlooks is that all kinds of critters are working late fall, winter, and early spring to decompose those leaves into tiny piece, which are further decomposed by the bacteria and fungi already in the soil. Earthworms live under the surface of the leaves and contribute to the shredding process, and as they move through the leaves and the soil beneath it, they leave behind their castings with all of the microorganisms they contain. The result is better soil structure, more nutrient availability to plants either developing root systems over the winter or those new flower and vegetable starts which will be planted in the spring. And while they don’t have large amounts of NPK, the castings do have many of the micronutrients (magnesium, zinc, copper, zinc, iron, calcium, and sulphur) which are also necessary to healthy plant development.

Earthworms are not the only insects which aid the decomposition of plant material. The centipedes in our yards, along with the beetles, work to reduce leaf material making it more accessible to the microorganisms in the soil. And, like earthworms, they burrow in the soil, creating pathways for roots and air and water, ensuring that the soil in our yard does not become compact and potentially anaerobic. Pill bugs, which are not technically bugs, but are crustaceans, can pull harmful heavy metals (like lead, cadmium, and arsenic) out of the soil and reduce their levels in the groundwater that makes nutrient uptake possible.

All of this decay takes place in the presence of oxygen, and so they will off-gas carbon dioxide. But throw bags of leaves in a landfill, let them get smushed under all that weight, and their environment quickly become anaerobic. They no longer produce carbon dioxide as they decompose, but methane, and according to the Environmental Protection Agency, methane is 28 times more potent as a greenhouse gas as is carbon dioxide. Admittedly the few bags of leaves that one might put on the curb won’t curb global warming significantly, but why contribute to the problem at all if we can just leave the leaves?

The leaves in our yard also provide habitat for those tiny critters that overwinter in our area. We love the luna moth, but most of us don’t know that our leaves will contain the cocoons or chrysalises of that moth as well as a few butterflies. We’ve already mentioned beetles. They continue to breed over the winter, and their babies need shelter, not to mention some other insect larva to eat. Firefly eggs will overwinter in our yards before entertaining us on those warm spring nights. And, given our attention to raising bees in MG of DC, we should know that queen bumble bees use the warmer ground under the leaves to wait until it’s warm enough to go look for a place to start a new brood. She is the only one who survives, so if we remove her habitat, we remove the potential offspring who will become the next generation of pollinators!

Food, shelter, soil improvement, insulation, weed suppression, pathways through our properties, leaves are not litter. They perform important services in our flower beds and lawns. If you use chopped leaves for your compost, by all means run your lawn mower or use your leaf shredder to get some for the pile. But think seriously about leaving most of the leaves intact and rake them into areas you want to plant in next spring, make some leaf mold (a rich soil amendment) create habitat for small mammals and amphibians, if you have them. And when the spring arrives, and you see the birds looking sideways at the ground, and using their feet and beaks to throws things out of the way, remember they are looking for the food you have generously provided them as those insects, living in the leaves, have nourished your soil.