Centipede grass is like a teenager. It won't clean out your refrigerator, or ask you to drop it off a block from the party, but it would prefer you just left it alone.
Most lawns in the Lowcountry are centipede grass because it's inexpensive and low maintenance. However, overmanaging our centipede lawns is what causes problems.
If you have teenagers, you know what overparenting looks like. Here's some quick, Dr. Phil advice on how to raise our lawns:
Nitrogen boosts growth and improves color. Centipede, however, prefers less nitrogen than St. Augustine, zoysia and Bermuda. General recommendations are to apply a half pound of nitrogen per 1,000 square feet in May and again in August. Over-fertilizing centipede is what leads to thatch and disease.
Most turf grasses exhibit a lush green color when fertilized. Under normal circumstances, centipede is bright green.
Because dark green is often associated with higher quality, efforts to darken the color with nitrogen can lead to problems because it stimulates growth. This is especially a problem when nitrogen is applied in the fall. If you're not a fan of centipede's Granny Smith color, iron will darken it without creating problems.
Potassium improves tolerance to drought and temperature extremes. In the Lowcountry, potassium is frequently deficient in soil.
An ideal fertilizer would be a slow-release containing equal parts nitrogen and potassium and little to no phosphorus, such as a 15-0-15. This was once a phosphate mining area so, unlike potassium, phosphorus is rarely deficient in the Lowcountry. Under normal circumstances, it's not required in fertilizer.
A soil test will reveal pH problems and nutrient deficiencies. If pH is low, it will affect the availability of certain nutrients, in particular minor nutrients such as iron.
Low pH is easily remedied with an application of lime. A soil test will recommend a lime application rate. High pH is much more difficult to correct because of the soil's buffering capacity. Many recommendations are to apply frequent applications of sulfur.
Thatch, the spongy layer of undecomposed organic matter, builds up as a result of fertilizer and regular irrigation. Grass clippings do not contribute to thatch and, in fact, return nutrients to the soil.
Burning dead top-growth in late winter does not reduce thatch, either. If you fertilize very little or not at all and only irrigate on an as-needed basis, thatch isn't likely to be a problem.
Thatch layers thicker than half-inch increase environmental stress and disease. High nitrogen applications are one of the major causes of excessive thatch.
Core aerification is an effective treatment. Aerifiers punch holes in the soil that physically remove thatch while stimulating root growth and boosting the activity of microbes that feed on thatch. Core aerifiers can be leased from local equipment rental dealers and can be done any time of the year.
Dethatchers, or vertical mowers, cut lines in the lawn that rip thatch out of the ground and stimulates horizontal growth via stolons and rhizomes. It's effective but much more stressful on the lawn than aerifying. Dethatching is generally recommended during spring to allow recovery before summer.
Centipede grass is susceptible to brown patch disease in late summer/early fall and again in spring. It is likely to occur in damp, shady conditions. Nitrogen can exacerbate brown patch, so cut back on fertilizer or avoid altogether in susceptible areas.
Brown patch can be a couple to several feet in diameter and can begin appearing as early as August. Granular fungicides can be used to prevent or treat infected areas.
Occasionally, mole crickets or armyworms can be a problem during the summer. A soapy flush (1 ounce of dish soap per gallon of water) can be used to bring the insects to the surface to verify the cause.
Centipede grass will handle a moderate amount of shade and traffic. However, St. Augustine is the best shade grass. Bermudagrass is best choice for traffic, such as dogs, but it needs at least six hours of sunlight.
Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at tony. firstname.lastname@example.org.