Fall Leaf Cleanup: Should You Remove Leaves From Under Trees?

Every October, Calgary homeowners face the same ritual: raking, bagging, and hauling away mountains of fallen leaves. It is one of the most time-consuming yard tasks of the year, and it raises a fair question — is it actually necessary? Should you remove every leaf, or is there a better approach? The answer depends on where the leaves are and how many you have.

The Case for Leaving Leaves

In a forest, nobody rakes. Fallen leaves form a natural mulch layer that insulates roots, retains moisture, adds organic matter to the soil, and provides habitat for beneficial insects and organisms. This leaf litter is part of a tree's natural nutrient cycle — the minerals and nutrients the tree pulled from the soil to grow those leaves are returned to the earth as the leaves decompose.

Under your trees, a moderate layer of leaves provides many of the same benefits. Leaves break down over winter and early spring, feeding the soil biology that keeps your trees healthy. Earthworms pull leaf fragments into the soil, improving structure and drainage. Beneficial insects overwinter in the leaf layer — including pollinators, predatory beetles, and other species that help keep pest populations in check.

The Case for Removing Leaves

While leaves are beneficial under trees, they can cause problems on your lawn. A thick mat of wet leaves smothers grass by blocking sunlight and trapping moisture. This creates ideal conditions for snow mould, a fungal disease that is extremely common in Calgary. If you have ever noticed grey or pink patches on your lawn in spring, snow mould is likely the culprit — and a blanket of unraked leaves over winter makes it worse.

Leaves also need to be cleared from certain areas for practical reasons:

• Gutters and downspouts: Clogged gutters cause water to back up against the fascia and can lead to ice dams in winter.
• Garden beds with perennials: A thick layer of wet leaves can smother low-growing perennials and ground covers. A light layer is fine and even beneficial.
• Driveways and walkways: Wet leaves on concrete and pavers are slippery and become a safety hazard once they freeze.

The Best Approach: Mulch-Mow Your Lawn

Rather than raking everything and throwing it away, the most practical approach for most Calgary homeowners is to mulch-mow their lawn. Run your mower over the fallen leaves with a mulching blade, which chops them into small pieces that settle between the grass blades and decompose quickly.

Research from multiple university turf programs has shown that mulch-mowing leaves into your lawn does not harm the grass. In fact, it adds organic matter and nutrients that improve soil health over time. The key is to keep up with leaf fall — mow weekly during peak drop to prevent the leaf layer from getting too thick for the mower to handle effectively.

If you have large trees that produce more leaves than your lawn can absorb, mulch-mow what you can and rake or blow the excess into garden beds or compost. The goal is to avoid thick, matted layers on the grass while still keeping the organic matter on your property.

Composting What You Collect

If you do rake leaves, composting them is far better than sending them to the landfill. Leaves are an excellent source of carbon (the "brown" component) in a compost pile. Mix them with nitrogen-rich materials like grass clippings or kitchen scraps for faster decomposition. Whole leaves can mat together and decompose slowly, so shredding them first — even just by running over a pile with the mower — speeds things up significantly.

Calgary's green cart program accepts leaves, which are composted at the city's facilities and eventually made available as compost. This is a good option if you do not maintain your own compost bin.

Under Trees and in Beds: Let Them Stay

In garden beds and under trees, leave the leaves. They serve as free, natural mulch. If you find the look too messy, rake the leaves into a thin, even layer rather than removing them entirely. You can also top them with a light layer of wood mulch for a tidier appearance while still getting the benefits of leaf decomposition underneath.

If you have trees that drop leaves with known disease issues — such as black knot on mayday trees or leaf spot — it can be beneficial to remove those leaves to reduce the amount of fungal spores overwintering in your yard. This is a targeted removal, not a wholesale cleanup.

Timing Matters in Calgary

Most trees in Calgary drop their leaves between mid-September and mid-October, though some elms and lilacs hang on later. Try to do your final lawn cleanup before the first lasting snowfall, which in Calgary typically arrives in late October or early November. Leaves trapped under snow all winter are the ones most likely to cause snow mould problems.

A quick fall cleanup paired with a final mulch-mow gives your lawn the best chance of coming through winter in good shape, while still letting nature do its thing under your trees.