Skip to main content
Camilla Care

Spread the mulch evenly for the benefit of the plants – Chicago Tribune

Vaseline 4 weeks ago

Applying mulch is one of the easiest and best ways to help your trees and other plants, but doing it incorrectly can lead to problems.

“Mulch should form a flat, even layer over the soil,” says Spencer Campbell, Plant Clinic manager at The Morton Arboretum in Lisle. “It should never be piled in a pile, especially around a tree.”

When mulch is piled against the trunk of a tree, it can trap moisture against the bark, promoting decay. “When the bark rots away, the tree’s circulation is cut off,” Campbell said. “It can lead to the death of the tree.”

A pile of mulch can also provide shelter for harmful insects and barking small animals such as voles, giving them perfect cover to nibble on. Young trees have bark that is thin and soft, easy to chew and rotten quickly, making them especially vulnerable to the dangers of piled mulch.

To avoid these problems, spread the mulch in an even layer over a large area, making sure it remains at least 2 inches (5 cm) away from the bark surrounding the tree’s trunk.

Spread properly, mulch plants do a world of good because it protects and nourishes the soil where their roots live. Mulch insulates the soil against extreme heat and cold. In hot weather it reduces evaporation to keep the soil moist. As the mulch decomposes, it releases nutrients into the soil and feeds microorganisms that improve conditions for your plants’ roots. Arboretum research has shown that trees surrounded by a large area of ​​mulch grow faster and more vigorously.

That mulched area protects the tree in another important way: It keeps lawn mowers and string trimmers away from the bark so they don’t damage it.

Mulch is powerful for all plants, not just trees, because it mimics the layer of leaf litter that their roots live under in nature. Fallen leaves, dry stems and dead branches accumulate throughout the seasons. Gradually, soil-dwelling organisms, including insects, fungi and bacteria, consume that waste to break it down and mix it to create rich, light soil. “When we spread mulch, we’re just trying to mimic what plants have been doing for themselves for millions of years,” Campbell says.

The commercial mulch sold in bags or by the cubic yard consists of shredded wood, but any plant material can be used as a mulch. “The leaves that fall each fall make a beautiful mulch,” he said. “That is what the trees in the forest depend on.”

Larger pieces, such as commercial shredded wood mulch or tree trim wood chips, will break down more slowly. Thinner or smaller types of mulch, such as straw or dried leaves, will decompose more quickly. “They will improve your soil faster, but you will also have to renew the mulch more often,” Campbell said.

These lighter mulches are the best choice for vegetable gardens that are replanted annually. “For vegetables, you want a mulch that will break down over the course of the year,” he said. Spread the mulch in an even layer about 4 to 5 inches deep around trees and shrubs, remembering to keep it away from their bark. Make the mulch area as large as you can, although it doesn’t have to be a perfect circle. In perennial and vegetable beds, a layer of 2.5 cm deep is sufficient.

Don’t forget to apply a light mulch around annual flowers and even in containers. “It will keep their potting mix from drying out as quickly,” Campbell said. “All plants benefit from a nice layer of mulch.”

For advice on trees and plants, contact the Plant Clinic at The Morton Arboretum (630-719-2424,, or [email protected]). Beth Botts is a writer at the Arboretum.