Darrell Blackwelder: Avoiding mulching mistakes

Published 12:00 am Saturday, May 31, 2025

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A friend of mine is so excited that her husband purchased her a truckload of fresh, new mulch. Fresh mulch can turn a drab, lackluster landscape into a flowing master design in just a matter of a few minutes. A layer of mulch also protects trees and shrubs from freezing weather and helps maintain moisture during dry weather. However, some mistakes are made applying to landscapes and other areas. Below are a few major mistakes.

Too much mulch: Using more than 6 inches of mulch often blocks air and water from reaching the soil and root system. Excessive mulch also invites insect and fungal disease problems. Applications of 4-6 inches of pine bark or other mulches are recommended for trees and shrubs.

Volcano mulching around trees: Mulch is often artfully piled high (mulch volcanoes), a foot or more, against the trunks of the trees in and around Salisbury landscapes. Excessive application promotes root expansion in the mulch and not into the soil. This can be a problem in poorly drained soils or during droughts.

Plastic mulch in landscapes: Using black plastic mulch in landscapes around shrubs and trees to control weeds is a bad idea. It prevents water and oxygen penetration to the roots, initiating stunted plant growth. Perennial weeds such as bermuda grass and nutsedge will eventually grow through plastic mulch becoming a nightmare to weed. Porous ground cloth allows water to penetrate, and limits weed growth, however some weeds eventually emerge through the material.

Some plants prefer different types of mulch: Annual and perennial plantings do much better when mulched with fine ground pine bark rather than pine needles. Applying pine needles often damages the plants and the annuals look much better with fine mulch.

Un-composted mulch: Un-composted mulch with sticks of green wood attracts many insects including termites. Decaying green wood also robs the plants nutrients during the decomposition process. Applying mulch with ground bark and wood should be well composted before application.

Darrell Blackwelder is the retired horticulture agent and director with the North Carolina Cooperative Extension Service in Rowan County. Contact him at deblackw@ncsu.edu.