Bark mulch OK. Plastic? Not so much

Published 12:00 am Friday, November 15, 2013

SALISBURY — Mulch has now become an essential part of landscaping. It can often turn a drab landscape into a flowing master design in a matter of minutes. Cooperative Extension frequently receives questions from homeowners about implementing mulch into their landscape designs. Below are considerations when adapting mulch into your landscape.
How much pine bark do I use? Bark mulch is often piled high, almost a foot, against the trunks of the trees in and around Salisbury. Does it matter how much bark mulch is used around a trees and shrubs? Excessive application of mulch can result in a situation in which roots are growing in the mulch and not in the soil. This can be a problem in poorly drained soils or during droughts. Excessive mulch also invites insect and fungal disease problems. Applications of 3 to 6 inches of pine bark or other mulches are recommended for trees and shrubs. Pull the mulch back 6 inches from the stems and trunks of trees.
Pine needles: Is there an advantage to using long leaf pine needles over other types of pine needles? Long leaf pine needles tend to last longer than loblolly or shortleaf pine needles. The longleaf pine contains wax within the cell that gives the surface a shiny finish and keeps them from deteriorating over a long period of time.
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, causing plants to become stunted. Weeds such as Bermuda grass and nutsedge often grow in the plastic, becoming a nightmare to weed. Some ground cloths that allow water to penetrate may work, but neither will control weeds.
Termites: Many associate termites with using bark mulch around shrubs near the house. Termites will not feed on bark. They will, however, feed on live wood often found in pine bark and other types of mulch. Applying any type of fresh green wood mulch that is not well composted near the home may attract termites. If the mulch stays overly moist, it may also attract termites.
Mulch will control weeds: Mulch will suppress weeds but not control them. Bermuda grass and other weeds will grow right through mulching materials. Hard to kill weeds such as Bermuda, nutsedge and others should be controlled before mulch applications.
Herbicides in mulch: There are commercial mulches available that have pre-emergence herbicides impregnated into the wood fibers. It is usually dyed wood mulch that will keep emerging weeds at bay for about two months. It is a good deterrent for most weeds if you have a severe weed problem.
These are just a few inquiries about mulching in the landscape. Go to and for more detailed information on using mulch in the landscape.

Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. Call 704-216-8970.