University of Illinois Extension
Using Fallen Leaves
 

[October 17, 2019]    Now that we’ve had some cooler temperatures (to go along with shorter days), we’re starting to see the leaves change color. In the next few weeks, we can look forward to our landscapes being awash in yellows, oranges, and reds. As the saying goes, though, all good things must come to an end. Eventually, all of those leaves will end up on the ground, and we’ll begin our annual battle of what to do with them.

If you only have a light covering of leaves in your lawn, they can be mowed. It’s best to mow leaves when they are dry, so they don’t clump together and make it more difficult to mow. When mowing leaves, make sure you can see the grass beneath the cut-up leaves. If the leaf layer is too thick, it can smoother and kill the grass. By mowing the leaves and chopping them into small pieces, they will drop between the blades of grass to the soil surface. Once there, microbes can begin to break them down. As the leaves are broken down, they will contribute to the organic matter present in soils and nutrients will be released for turf to utilize.

If you have too many leaves to mow, consider incorporating some into your garden beds. Adding a 6 to 8-inch layer of leaves and incorporating (tilling) them into garden soils can help improve them by increasing organic matter. In heavy clay soils, this will help with drainage and aeration, and in sandy soils, it will improve the soil’s ability to hold onto water and nutrients. If you decide to incorporate leaves into garden beds, its best to do this in the fall. This will allow for plenty of time for the leaves to break down (leaves have a high carbon to nitrogen ratio and can take a while to break down) before you plant in the spring. If you want to speed up the decomposition process, you can add some fertilizer to the soil after the leaves have been incorporated.

Leaves can also be used as a mulch in vegetable gardens, flower beds and around trees and shrubs. As you may know by now, a layer of mulch can be rather beneficial in our landscapes. It can help conserve soil moisture, moderate soil temperatures, prevent soil crusting and erosion as well as helping to control weeds. In the case of leaves, and other organic mulches, they can also contribute nutrients and organic matter to soils as they break down. When using leaves as mulch, it's a good idea to shred them first because leaves may clump together, forming a mat that can prevent moisture from reaching the soil. Shredded leaves also are more likely to stay in place compared to unshredded leaves.

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Leaves can be used to help insulate plants too. By using leaves as insulation, we can keep the soil uniformly cold and prevent freezing and thawing cycles that can damage marginally hardy plants (some hybrid tea roses, lavender, etc.). This can be done by placing shredded leaves around the crowns of these plants, or wire frames can be built and filled with leaves. If using leaves as insulation, don’t put them on plants until temperatures are consistently below freezing.

If you’ve ever done any composting, you know how valuable leaves can be as a 'brown' material. For the uninitiated, compost is a dark, crumbly, and earthy-smelling form of organic matter that has gone through a natural decomposition process. If you have a garden, lawn, trees, shrubs, or even planter boxes or houseplants, you have a use for compost. If you’re interested in learning more about compost, you can find several different resources here:  https://extension.illinois. edu/global/composting-resources.

While we often dread the appearance of leaves in our yards, they are a valuable and free resource for our landscapes. Before you use up all of your leaves, take some time to make a big pile of them, and relive your childhood.

Good Growing Tip of the Week: While we’re often in a hurry to clean up leaves in the fall, they can be important overwintering areas for a variety of wildlife. Many different types of insects, such as butterflies and bees, as well as other animals such as salamanders and toads, will rely on leaf litter as habitat to make it through the winter. To conserve these animals consider leaving part of your yard as is until spring.

[News Source: Ken Johnson, Horticulture Educator, University of Illinois]