COLUMN: To mulch or not to mulch

By: Amanda Taylor | Statesville Record & Landmark
Published: October 17, 2011

Healthy plants are less susceptible to environmental stresses, like excessive heat and drought, as well as insects and diseases. One of the easiest ways to encourage healthy plants in the landscape is to mulch them.
There are many benefits of mulching, including weed suppression, moderation of soil temperature and moisture, and less erosion. Mulch can also decrease the incidence of soil-borne diseases by preventing soil-borne pathogens from splashing onto leaves. Additionally, mulching around trees will prevent possibly fatal trunk damage caused by mowers and weed eaters.
There are two types of mulches — organic mulch (made from material that was once living) and inorganic mulch. The most common types of organic mulch are pine bark mulch, hardwood mulch, and pine needles. Inorganic mulches include lava rocks, pebbles, plastic, and landscape fabric.
Organic mulches are preferred over inorganic mulches, because they break down and release nutrients back to the soil, which plants can then take up. They can also improve soil structure by adding organic matter. Because organic mulches break down, they need to be replenished periodically.
Inorganic mulches do not break down, so they don’t need to be replenished, but they also do not contribute anything to the soil. If you’ve ever had to replant an area that had a mulch of lava rock or pebbles, then you know what a pain it can be to remove the rock.
Although mulching can be an easy and inexpensive component of growing healthy plants, many plants are mulched incorrectly, which can damage plants more than it helps them.
A common mistake is creating “mulch volcanoes,” where several inches of mulch is piled against the trunk of a tree. It is believed that this method of mulching promotes trunk decay and encourages shallow roots at the expense of deep root development. The lack of deep rooting can contribute to trees blowing over during storms and their inability to cope with drought stress.
Trees and shrubs in the landscape should be mulched with a 3- to 4-inch layer of organic mulch, with the mulch pulled at least a couple of inches away from the base of the tree. A tree’s root system is extends to an area considerably past its drip line (imagine a line drawn straight down from a tree’s canopy to the ground), so mulch as large of an area as possible beneath the tree. Check the mulch annually and replenish as needed to maintain the correct depth.
For more information on gardening and landscaping, visit the Iredell County Cooperative Extension Service’s website at http://iredell.ces.ncsu.edu/.

Amanda Taylor is an agriculture agent (horticulture) with the NC Cooperative Extension Service in Statesville.