Landscape mulches of different types are evaluated in research plots at the LSU AgCenter Hammond Research Station. (Photo by Allen Owings. Click on photo for downloadable image.)

New landscaping around a bed of azaleas is enhanced by mulch at the LSU AgCenter Hammond Research Station. (Photo by Allen Owings. Click on photo for downloadable image.)

News Release Distributed 12/07/12

HAMMOND, La. – As we approach the end of fall and the beginning of winter, we may have oak leaves and pine needles lying around in our landscapes in abundance. What can we do with these products? How about using them for mulch in our landscape beds, around our trees and in our vegetable gardens? Sometimes leaf litter, pine straw and similar materials are called “Mother Nature’s mulch.”

Mulching is one of the landscape practices most home gardeners follow several times during the year. So let’s review the use of mulch in the landscape and how to properly apply it to achieve maximum benefit.

Mulching is a great sustainable landscape practice when done correctly.

A mulch layer around trees and shrubs as well as in planted beds and covering bare ground provides many benefits. In areas that are difficult to mow, irrigate or otherwise maintain, mulch replaces turf or groundcovers. It also serves a similar purpose in shady areas where many plants don’t grow well.

Benefits of mulching include:

– Organic mulch materials improve soil fertility as they decompose.

– Mulch buffers soil temperature, keeping soils warmer in winter and cooler in summer.

– Mulch helps maintain soil moisture by reducing evaporation. A layer of mulch also minimizes water needs for established plants.

– Fresh mulch inhibits weed germination and growth.

– Over time, many types of mulch improve soil aeration, structure and drainage.

– A mulch layer can inhibit certain plant diseases.

– Mulch around trees and shrubs (but not against the trunk) eases maintenance and reduces the likelihood of damage from string trimmers.

– Mulch gives planting beds a neat and uniform appearance, adding a contrast of color and texture that complements plantings.

Follow these tips when adding mulch to your landscape:

– For well-drained sites, apply a 2-inch to 3-inch layer (after settling) of mulch around trees, shrubs and bedding plants. If there are drainage problems, use a thinner layer. Coarse materials, such as pine nuggets, may be applied to a depth of 4 inches, but don’t allow mulch to accumulate more deeply. If mulch is already present, check the depth. Do not add mulch if there is a sufficient layer in place (2 inches to 3 inches).

– “Volcano mulching,” or mulch applied too deeply, hinders oxygen exchange to roots, which stresses the plant and causes root rot. Do not place mulch on top of a tree’s root ball or against the trunk. More than about 1 inch of mulch on the root ball of newly planted trees and shrubs can stress plants because mulch can intercept water meant for the roots.

– If mulch is piled against a tree trunk, pull it back several inches to uncover the base of the trunk and the root flare. Mulch piled against tree trunks holds moisture against the trunk and stems, and trunks that remain constantly wet are prone to root rot. Mulch piled high against the trunks of young trees also may create habitats for rodents that chew the bark and can girdle the trees.

– Mulch out to a tree’s drip line or beyond – at least an 8-foot diameter around the tree. Remember that in a forest environment, a tree’s entire root system (which usually extends well beyond the drip line) would be mulched naturally.

– Thick blankets of fine mulch can become matted and may prevent water and air from seeping through or become like potting soil and support weed growth. Rake old mulch to break up any matted layers and to refresh its appearance.

– Organic mulches may require weeding and replenishment once or twice a year to maintain a total depth of 2 inches to 3 inches.

– Shells, crushed stone or pebbles can be used as mulch, but they won’t contribute to the soil’s nutrient and organic content or water-holding capacity. Limestone and shells both raise soil pH, though, and they reflect heat, increasing the water needs of plants.

You can see more about work being done in landscape horticulture by viewing the LSU AgCenter Hammond Research Station website. Also, like us on Facebook. You can find an abundance of landscape information for both home gardeners and industry professionals.

Rick Bogren