Don't Just Leave Your Leaves

It is fall, which means a lot of things, but one of my favorites is large leaf piles to jump in. What to do with these leaves is something I’ve been figuring out over the past few years, and a lot of the advice I’ve gotten hasn’t worked out well for me. Many conservationists are advocating leaving leaf piles to break down in your yard, and are listing quite a few really meaningful reasons to do it. Taking leaves out of your yard and then adding fertilizer is a lot of steps for the same results, and fallen leaves can provide habitats for overwintering animals. But leaving leaf piles to break down naturally can have very different effects depending on where you live.

In places like the Midwest where winters tend to be long and wet instead of crisp and snowy, such as much of Ohio, leaf piles often don’t decompose the way you might hope. Instead of breaking down into a nice layer of organic matter, they can turn into a slimy mat that smothers plant roots and doesn’t create the best environment for overwintering wildlife. Here’s why this happens and what you can do about it.

Why Wet Winters Aren’t Ideal for Leaf Breakdown

In the Midwest, those long stretches of damp weather can waterlog leaf piles. This slows down decomposition because it limits oxygen—something microbes need to do their job effectively. Instead of a healthy, crumbly mulch, you end up with a heavy, compacted mess that can:

• Smother grass and plant roots, blocking them from getting air and sunlight.¹
• Create poor insulation for critters like insects and amphibians, since soggy leaves don’t provide the dry, warm spaces they need to overwinter.²
• Harbor mold and fungi, which can be harmful to nearby plants, especially if the leaves sit near tree trunks or shrub bases.³

This is a stark contrast to regions with crisp snowfall or milder winters, where leaves can dry out and decompose more easily.

How the Midwest Compares to Other Regions

Wet winters are not unique to the Midwest, but they do make things tricky:

• Northeast: While there’s plenty of rain here, consistent snow cover in northern parts can insulate leaves and create better conditions for decomposition.⁴
• Pacific Northwest: Similar challenges occur because of the near-constant winter rain, leading to slow, slimy decomposition.
• Mountain West: The crisp, dry snowfall here keeps leaves from compacting, so they often break down more naturally.
• Southeast: The mild winters and faster decomposition make leaf piles more beneficial, as they’re less likely to mat and more likely to support wildlife.

What You Can Do

If you’re dealing with those Midwest winters, here’s how to avoid the slimy mat problem while still benefiting from your leaves:

1. Mulch the Leaves
   Run a mulching mower over the leaves and spread them out thinly on your lawn or garden beds. This speeds up decomposition and adds nutrients to the soil without creating a suffocating layer.⁵

2. Compost the Leaves
   Set up a compost pile! Combining leaves with other organic materials gives you more control over the breakdown process and avoids the slimy mess altogether.⁶

3. Create Wildlife-Friendly Piles
   If you’re aiming to help overwintering critters, create smaller, dispersed leaf piles in less trafficked areas of your yard. Keep them away from tree trunks or sensitive plant roots.⁷

4. Use Leaves as Winter Mulch
   Spread leaves loosely around perennials or shrubs to insulate roots. Just fluff the leaves occasionally to keep them from matting.⁸

By managing your leaves thoughtfully, you can support your yard’s health and local wildlife, even in the Midwest’s wet winters!

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References

1. Cornell University Cooperative Extension. (2021). Managing leaves: How to turn autumn leaves into gardener’s gold. Retrieved from https://ccetompkins.org/resources/managing-leaves
2. National Wildlife Federation. (n.d.). Gardening for wildlife in fall and winter. Retrieved from https://www.nwf.org/Garden-for-Wildlife/Why-Garden-for-Wildlife
3. University of Minnesota Extension. (2020). What to do with leaves in the yard? Retrieved from https://extension.umn.edu/planting-and-growing-guides/what-do-leaves-yard
4. Haskell, D. G. (2012). The forest unseen: A year’s watch in nature. New York, NY: Penguin Books.
5. Pennsylvania State University Extension. (2022). Mulching leaves: A healthy choice for your lawn. Retrieved from https://extension.psu.edu/mulching-leaves
6. Environmental Protection Agency. (n.d.). Composting basics. Retrieved from https://www.epa.gov/recycle/composting-home
7. National Audubon Society. (n.d.). Creating habitat in fall and winter. Retrieved from https://www.audubon.org/conservation/creating-habitat-fall-and-winter
8. USDA Natural Resources Conservation Service. (n.d.). Using leaves as mulch. Retrieved from https://www.nrcs.usda.gov/resources/guides-and-factsheets