Campus News

Avoid mulch ‘volcano’ in landscape

In many manicured landscapes, plants often seem to grow out of little mulch volcanoes. But piling mulch 1 to 3 feet deep around trees is way too much of a good thing, experts say.

“Piling mulch around the base of the plant does more harm than good,” said Gary Wade, a Cooperative Extension horticulturist with UGA’s College of Agricultural and Environmental Sciences. “It generally sets the plant up for long-term stress, which makes it more prone to injury from insects, diseases and environmental extremes.”

Mulches keep the roots evenly moist, insulate roots from extreme heat and cold, prevent weeds that compete with plants for moisture and nutrients and serve as a barrier to certain soil-borne diseases.

“Done properly,” Wade said, “mulching is one of the best things you can do to help plants get established and survive our environmental extremes.”

But there’s a right way to do it, he said. And making mulch volcanoes isn’t it.

The key to proper mulching is to take a good look at how nature mulches plants. The natural mulch of fallen leaves is flat and rarely more than 2 inches thick. It never looks like a volcano. A 6-inch layer of bark will last a long time, Wade said. But it may restrict gas exchange in the soil and may keep the soil too wet during rainy periods. A mulch layer 3 inches deep after settling is enough for most plants. If you can, extend the mulched areas out to the outermost leaves (called the drip line) and beyond. And pull the mulch back a few inches from the main trunk.

Mulching properly will help keep your plants healthy, Wade said. Mulch volcanoes can have the opposite effect.