Leaves, glorious leaves! They twirl from the trees, drift on the sidewalk, rustle underfoot. And in your garden, they do wonders.

“There are many ways you can use autumn leaves to help your plants and improve your home landscape,” said Julie Janoski, Plant Clinic manager at The Morton Arboretum in Lisle. “And the best part is, they’re free.”

In a natural environment, every plant lives under a layer of last year’s decaying leaves and stalks, which insulates and protects their roots, provides essential nutrients, and builds up the soil. Gardeners can use the leaves they collect to accomplish the same things.

Here are some ways to make the most of this colorful treasure of fall.

Use them for mulch. Mulch is a layer of any kind of plant matter that covers the soil, imitating the leaf litter that develops in nature. The Arboretum uses leaves collected on-site to mulch the perennial beds in all its gardens. “They’re light and fluffy, so they make good insulation against temperature extremes in winter,” Janoski said. By spring, leaf mulch will partly breakdown. “That’s a good thing,” she said. “It means that microorganisms in the soil are consuming them and releasing valuable nutrients for your plants’ roots.”

Rake them where you want them. You can move whole leaves over from your lawn over to act as mulch on perennial beds or around shrubs. Rake most of them off the grass, because a matted layer of whole leaves can smother the grass plants.

Shred them if you like. Shredded leaves look tidier and won’t blow around when used as mulch. They also breakdown 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. When you carry them off to use for mulch or compost, leave some shreds on the grass and rake them out evenly. They will decay and improve the soil of the lawn.

Improve your soil. “Leaves are a free and abundant source of organic matter,” Janoski said. Organic matter — basically, dead plants — makes the soil a better environment for plant roots. It gives soil a more open texture, feeds those valuable microorganisms, provides nutrients, and acts like a sponge to hold moisture. If you use leaves as mulch, you will add organic matter as it breaks down. You can also use shredded leaves as a soil amendment when preparing new beds.

Make compost. Compost is partially decayed plant matter, broken down by natural soil organisms. It’s a powerful and convenient way for gardeners to distribute concentrated organic matter where they want it, and it has many uses in the garden. “Fall is a great time to start making compost because you have an abundance of leaves to start with,” Janoski said. To learn more about the process, see mortonarb.org/composting.

Insulate. Use leaves as insulation against autumn freezes and winter cold. A layer of leaves can protect late vegetable 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 so you can pull the crops a little later. “It can prolong your harvest in autumn,” she said. Leaves also make good insulation around tender ornamental plants such as hybrid tea roses.

Keep a stash. In an out-of-the-way spot, pile up a bunch of leaves to use next spring and summer. You can use them to replenish mulch in beds or to mulch next year’s vegetable garden, and you will have a steady supply to feed into the compost pile. Shredded leaves will be much more compact than whole leaves, allowing you to stash more away.

“Don’t just think about cleaning up autumn leaves,” Janoski said. “Think about using them. They’re too valuable to waste.”

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.

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