Pushing centipedegrass to the brink of disaster

Our typically erratic late winter temperatures may have your centipede pushed to the brink of disaster. We have problems just about every year with low temperature injury during the spring “green up” period. Keeping the nitrogen rates low, avoiding pre-emergence herbicides, and mowing at the right height can help minimize these “winter kill” problems.

One thing we’ve always known about centipede grass is that it will initiate new growth quickly with just a couple of days of favorable temperatures. Once this happens, temperatures of 19 degrees will kill it. Temperatures in the low 20s–especially when accompanied by wind–may do serious damage. Because we can’t control the weather, some damage is inevitable, but you can manage your lawn well to minimize the problems.

Start with the nitrogen rates. Apply no more than one pound of actual nitrogen per 1,000 square feet each year. Consider two applications of one-half pound each in late April and late June. Fertilizers such as 5-0-15, 5-0-20, 5-5-15 or 5-5-20 work well when applied at 10 pounds per 1,000 square feet. Avoid nitrogen applications before the middle of April and after the middle of August.

Some folks complain that a fertilizer program like this just doesn’t give them centipede with nice, green color. Unfortunately, centipede is supposed to be apple-green. If you must have a little more green, foliar applications of chelated iron will darken the color without promoting too much growth.

Leaving your centipede a little shaggy is another factor in low temperature problems. Keeping the mowing height below one and one-half inches helps the stolons (above-ground stems) stay close to the soil surface. It also helps prevent the accumulation of lots of thatch. Mowing heights above 2 inches have been found to aggravate winter-kill.

Speaking of thatch, if you’re doing the mowing and fertilizing right, you shouldn’t accumulate excessive thatch in a centipede lawn. Thick, thatchy centipede lawns are almost always over-fertilized and mowed too high. That also means that–in most cases–there’s no compelling reason to aerate centipede lawns. Severely compacted soils are certainly an exception, though.

Centipede also struggles with crabgrass-preventing herbicides such as pendimethalin, Barricade and Dimension. These products are very effective on the weeds but tend to prune the roots of centipede. Consider dropping the pre-emergence herbicides to avoid this problem. If the crabgrass starts to take over, you do have the option of applying sethoxydim (Vantage) later in the season.

These management strategies apply only to centipede. If you’re growing Bermuda or zoysia, the recommendations are very different.

Cooperative Extension has lawn maintenance calendars for all of the popular grasses. Check on its Web site at www.brunswick.ces.ncsu.edu/ or call 253-2610.