Mulch is as important to southern gardens and landscapes as sausage gravy is to biscuits or as corn bread is to pinto beans. Despite our record rainfall this spring and summer, mulch is still the right thing to do. A shallow layer of organic mulch conserves moisture, suppresses weeds, and supplies nutrients as it decomposes. Covering bare soil with mulch reduces erosion. Most importantly, mulch enhances the appearance of our plantings—it makes our plants pop.
A common question that arises is which mulch is best? My answer: anything that looks good and is affordable. During my travels throughout the South I’ve seen a wide variety of mulches used by gardeners. They include newspapers, old carpeting, salt hay, cocoa and pecan hulls, and eucalyptus chips. Mulch, in my opinion, is a lot like barbecue sauces: there are regional differences. For example, pine straw is commonplace from the Midlands to the Carolina coast. Along the coast, besides pine straw, you’ll find seashells, white marble chips, and pea gravel. In the Piedmont shredded hard-and softwood mulches are commonplace.
Colored woody or rubber mulches are in vogue right now. Tired of earth tones, then consider mulches made of recycled tires in “Bright Blue” or “Real Teal”.
Whatever mulch you apply, apply it properly by following these simple guidelines:
Apply a shallow 2 to 4 inch layer of mulch. For annuals and perennials, apply a mulch layer one to two inches thick. Avoid the temptation to create a “mulch volcano” that’s a root-suffocating two to three feet high with sloped slides. Volcano mulching will not impress passersby (“Hey, look everybody, Bob mulched his trees!”), but it can kill trees. The bark of shrubs and trees needs to “breathe” and it needs to be dry. Keep the mulch at least 3 to 6 inches away from the trunk of young trees and shrubs and 8 to 12 inches away from the trunks of mature trees. Also, by keeping the trunk free of mulch discourages bark-feeding voles which like to be hidden from predators.
Mulch individual trees out to their outermost branches or drip lines, if at all possible. Because the root system can extend two to three times farther than the branches of a plant, mulch as large an area as possible. To avoid Òslalom mowingÓ in and around individual plantings of trees, unite them with a single bed of mulch.
Every two or three years submit a soil sample from your mulched beds to have it tested for pH and fertility levels. Mulches, such as pine straw or pine needles, are high in nitrogen and phosphorus, but they also acidify the soil as they decompose. Florida researchers reported in the Journal of Arboriculture (March 1999) that a 3.5 inch layer of pine needles reduced the soil pH from 5 to 4.4 over the course of a year. While this makes pine straw an ideal mulch for acid-loving plants, other less acid-tolerant plants would benefit from the addition of calcitic or dolomitic limestone to increase the soil pH to the optimum level as recommended by the results of the soil test. Also, adjusting the pH to the right level will avoid potential nutrient deficiencies caused by a low soil pH, especially nitrogen, phosphorus, potassium, calcium, and magnesium.
So, if you’re looking for something to do in the landscape, throw some mulch around. And if you’re feeling really adventurous this year, toss out a Caribbean Blue colored mulch with a sprinkling of last summer’s seashells on top. Guaranteed, your neighbors will know that you’ve mulched your landscape .