Fallen leaves could be a useful tool in your garden

October is treasure time when golden leaves pile up like doubloons in a pirate’s chest.

“Autumn leaves are valuable for your garden and your plants,” said Spencer Campbell, Plant Clinic manager at The Morton Arboretum in Lisle. “Don’t waste them. Use them.”

The leaves that fall from trees and shrubs every year are nature’s way of enriching the soil in which plants grow. As leaves on the ground are consumed by fungi, bacteria, and other organisms in the soil, they release nutrients that plants need and improve the soil structure to make it a better home for plants’ roots.

Leaves are also nature’s insulation. In the woods there is always a layer of decaying leaves that protects plants’ roots from extremes of hot and cold and shelters seeds that will sprout and bloom in spring. “When we spread mulch in our yards, we’re just imitating what fallen leaves do in nature,” Campbell said.

Here are some tips from the Plant Clinic for making the most of the autumn bounty of leaves.

Use leaves for mulch. Simply rake fallen leaves onto perennial beds or vegetable gardens or around trees and shrubs. By spring, the leaves will have partly broken down and disappeared. That is the work of microorganisms in the soil that consume them and release their nutrients.

Rake most leaves off the lawn. A few leaves won’t hurt, but a mat of leaves left on the turf may encourage disease and will block the sunlight that the grass plants need.

Shred them if you like. Shredded leaves look tidier and won’t blow around when they are used as mulch. They also break down faster on the lawn or in a compost pile. To shred leaves, pile them on the lawn and run your lawn mower over them a couple of times. “It’s fine to leave some shredded leaves on the grass,” Campbell said. “They’ll break down quickly and improve the soil for your grass.”

Make compost. Leaves are a major ingredient in any successful compost pile. Mix them up with end-of-season annuals, weeds, and selected vegetable and fruit scraps from the kitchen. After a few months, you will have a versatile and powerful soil amendment. Learn more at mortonarb.org/composting.

Insulate. Use a layer of leaves as insulation against autumn freezes and winter cold, prolonging the fall harvest in a vegetable garden. They can protect late crops, such as cabbage or spinach, when an overnight frost is predicted. If you pile leaves over the beds of root vegetables such as carrots and beets, the soil will freeze more slowly, giving you more time to harvest the roots. Leaves also make good insulation around tender ornamental plants such as hybrid tea roses, contained by a cylinder of wire mesh or burlap.

Save leaves for later. Leaves are useful all year long as an ingredient in compost, a way to add organic matter to soil, or for mulch in next year’s beds or vegetable garden. Stow away as many as you can in an out-of-the-way corner or in a spare compost bin. Shredded leaves take up much less space than whole leaves, allowing you to stash more away.

For tree and plant advice, contact the Plant Clinic at The Morton Arboretum (630-719-2424, mortonarb.org/plant-clinic, or plantclinic@mortonarb.org). Beth Botts is a staff writer at the Arboretum.