St. Augustine GrassStenotaphrum secundatum
St Augustine grass is a perennial robust widely used for pastures and lawns. In the warmer climates of the tropics and subtropics it rivals bermuda grass in importance. It is a coarse textured, stoloniferous species that roots at the nodes. Unlike bermuda grass, St Augustine grass does not have rhizomes.
Use and Management
St Augustine grass is adapted to moist, coastal mild winter temperatures. It is known to be tolerant of high summer temperatures, and St Augustine retains its color at temperatures as much as 10 degrees lower than Bermuda grass. It tolerates moderate shade, being as good or better than other warm season grasses for shaded sites. However, under densely shaded conditions, it develops thin, spindly turf. So long as fertility and drainage are adequate, St Augustine tolerates a wide range of soil types. It does not tolerate compacted or waterlogged soil conditions. St Augustine grass is used primarily for lawns as it does not tolerate traffic as well as some other warm season species. It produces satisfactory turf at moderate levels of maintenance, effectively competes with weeds and other grasses and has only a few serious pests.
The growth rate is dependent on temperature, moisture availability and nutrient availability. Any one of these factors can limit the rate of growth of this species. In the spring with mild daytime temperatures and cool night temperatures, St Augustine greens up, but makes little growth. As day and night temperatures increase during late spring and summer, the growth rate increases. Thus, an established lawn may require mowing every 2 weeks in early spring and as often as every five days by late spring if nitrogen is applied. During the fall, as temperatures cool, St Augustine maintains its dark green color, but its growth rate declines sharply. Mowing frequency may be reduced to twice monthly during late fall and early winter.
Mowing heights may range from 1 to 3 inches depending on the frequency of mowing and the degree of shade present. At mowing heights below 2 inches, St Augustine grass should be mowed every five days during late spring ans summer. At 2 ½ inche mowing height, a 7-10 mowing schedule is adequate. Above 2 1’/2 inches it should be mowed at 10 – 14 day intervals. In moderate to dense shade, St Augustine should be mowed at about 3 “ at 10 day intervals.
During the fall, height should be raised about 1 inch to increase total leaf area of the turf. The increased leaf area will help the grass accumulate energy reserves to get through the winter. The greater leaf area will also help prevent weed invasion during the dormant season.
As long as St Augustine grass has been cultivated, it can be propagated by vegetative means – stolens, plugs or sod.
Several insect pests cause serious damage to St Augustine lawns. Chinch Bug, brownpatch and white grub worm. Chinch bug symptoms resemble drought stress – stunted, chlorotic spots in open (full sun) areas of the lawn. As feeding continues, irregular areas of dead grass develop in the lawn. Two to six insecticide applications are necessary to control cinch bugs.
White grubs are the larvae of the May beetle or June Bug that develop in the summer and fall just below the soil surface. The grubs feed on roots of St Augustine grass and cause significant losses of turf during some years. Damage usually appears the following year as dead areas of grass that can be easily lifted from the lawn. Grub control is difficult since the larvae are quite large and feed just below the soil surface. To be effective, insecticides must be applied to drench the soil where the insects feed.
St Augustine grass is susceptible to a number of turfgrass diseases including brownpatch, SAD, gray leaf spot, Helminthosporium, Pythium, rust, downy mildew and others. All of these, except SAD, are caused by fungi and can be controlled by good management and fungicides. SAD is a virus disease for which no chemical control. Only resistant varieties are effective against this disease. Floratam, Seville, and Raleigh have shown good resistance to the SAD virus. Raleigh is the standard variety for the DFW areas.
Brown patch and gray leaf spot are the most serious diseases caused by fungi. Although the diseases rarely kill St Augustine, they severely weaken and thin the grass to the degree that the lawn is unsightly. Preventive applications of fungicides are most effective against these diseases.
A healthy St Augustine grass lawn effectively crowds out most weeds. But St Augustine grass that is not properly maintained or is weakened by insects or disease can be invaded by grassy and broadleaf weeds. Cool season weeds such as henbit, chickweed and clover are a serious problem in dormant St Augustine grass. These weeds can be controlled by hormone-type herbicides in early spring.
Annual grassy weeds such as fescue, and annual bluegrass and crabgrass are best controlled by timely applications of preemergence herbicides. Perennial grasses such as dallisgrass and bermudagrass are difficult to control in St Augustine lawns. Nonselective products can be applied as directed sprays to these weeds to obtain control.
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