SPECIAL TOPICS: ST AUGUSTINE GRASS

ST. AUGUSTINE GRASS VARIETIES

There are a variety of types of St. Augustine grasses.


If you have an automatic sprinkler system, install a rain shut-off device or sensor that will override the system when adequate rainfall has occurred. Your water management districts, Cooperative Extension Service, USDA Natural Resources Conservation Service or an irrigation professional can provide technical assistance.
For best results, water in the early morning (4-7 a.m.). This is the most efficient time because temperature and wind speeds are at their lowest and evaporation is reduced. Also, grasses will be less susceptible to fungus if water is applied at the time dew normally forms.
Apply 1/2-inch to 3/4-inch of water when the grass shows signs of distress (bluish-gray color, folded leaf blades). Don't apply more water until symptoms reappear.
Experiment with gradual reductions in irrigation to see if plants can tolerate less water. Some people use no irrigation, yet have healthy plants. Water less in cooler months (November-March), and turn off automatic systems in the summer if rainfall is consistent.

Common and Roselawn. These are pasture types of St. Augustine grass that evolved in the 1800s. They produce a coarse, open turf that is susceptible to chinch bugs, herbicide damage, shade, and cold damage. They also have a light leaf color and do not respond well to fertilization. Avoid planting these cultivars if lawn appearance is important.

Bitterblue. This is an improved variety selected in the 1930s. Bitterblue has a finer, denser texture and darker blue-green color than common St. Augustine grass . It has improved cold tolerance and good shade tolerance but is not resistant to chinch bugs or gray leaf spot disease. Its tolerance to atrazine is also lower than other varieties, making weed control more difficult. Bitterblue can produce a good lawn under proper management practices and pest control.

Floratine. This is an improved selection from Bitterblue that was released in 1962 by the Florida Agricultural Experiment Station. It has finer leaf texture and a denser and shorter growth habit that allows closer mowing than common St. Augustine grass . It is not resistant to chinch bugs but tolerates light to moderate shade. Floratine's other characteristics are similar to Bitterblue's.

Floratam. Floratam is an improved St. Augustine grass that was released jointly in 1973 by the University of Florida and Texas A & M. Floratam is the most widely produced and used St. Augustine grass in Florida. It is a coarse-textured cultivar that has poor cold and shade tolerance. It will thin in direct relation to the amount of shade received. It grows vigorously in the warmer, but has a relatively long period of dormancy in north Florida and greens-up more slowly in the spring than some cultivars. It has some degree of chinch bug and SADV resistance, although new strains of chinch bugs that can damage Floratam have been identified. Floratam is tolerant of atrazine herbicides when temperatures are below 85°F.

Palmetto. Palmetto was a selection from a Florida sod grower in 1988. It was well received by sod growers throughout the southeast, but, unfortunately, little university research has been done to date on this cultivar. It is often described as highly tolerant of shade, drought, and cold, but no impartial evidence of these claims exists at this time. It does exhibit a shorter growth habit, similar to Jade, Delmar, and Seville.

Raleigh. Raleigh is a cold-hardy cultivar released by North Carolina State University in 1980. It has a medium green color with a coarse texture. It is susceptible to chinch bugs, but can be planted in northern Florida due to its tolerance to lower temperatures. It is also susceptible to brown patch disease. During peak summertime heat, Raleigh has been noted to yellow and to not grow as aggressively as during cooler temperatures. Supplemental iron applications can reduce this yellowing tendency. Raleigh is best adapted to the heavier, organic, clayey soils with medium to low soil pH in central and north Florida.

Seville. Seville is a semi-dwarf, fine-leaved variety with a dark green color and a low growth habit. It is susceptible to chinch bug and webworm damage, but resistant to SADV. Due to its compact growth habit, Seville tends to be thatch-prone and shallow rooting. Seville performs well in shade and full sun, but is cold sensitive. Its cold tolerance is similar to Floratine's. Being a semi-dwarf variety, Seville's maintenance is different than taller growing varieties.

Floralawn. This cultivar was released in 1986 by the Florida Agricultural Experiment Station. It is resistant to SADV, chinch bugs, sod webworms and brown patch. Like Floratam, it has poor shade and cold tolerance. It is also coarse-textured. Floralawn should be grown in mild environments in full sun to moderate shade under low to moderate fertility.

Jade and Delmar. These two semi-dwarf releases are commercially available as sod or plugs. Jade and Delmar have improved shade tolerance, shorter internodes, a darker green color, and better cold tolerance than Seville. They should be mowed at 1½-2½ inches. Jade has a finer leaf blade texture and better shade tolerance than Delmar. Delmar has enhanced cold tolerance; therefore, it can be grown in cooler regions of Florida. Jade and Delmar are both susceptible to chinch bugs, sod webworms, and brown patch disease. These also have slow lateral runner growth, thus, require longer periods for grow-in from plugs or recovery from damage.

Several other lesser known and available St. Augustine grass varieties have been released. These include FX-33, Sunclipse, Mercedes, Gulf Star and others. Research performed on these varieties has been limited and generally they have not proven superior to older varieties that are currently available.

For more information go to: http://edis.ifas.ufl.edu/LH010
St. Augustine grass for Florida Lawns. L.E. Trenholm, J.L. Cisar, and J. Bryan Unruh Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: May 1991. Revised: October 2000.

 

NEW ST. AUGUSTINE GRASS

While St. Augustine sod is the most shade tolerant grass type available in Florida it will not grow under shady conditions as well as if it were in full sun.

All commercially grown sod, even the shade tolerant varieties are produced in the full sun. As a result, new sod will always go through a transition period while it adjusts to the reduced light under your trees. This transition period can last up to a year.

New grass planted under deciduous trees (like Oaks that drop all or part of their leaves in the winter) has particular difficulty during this transition period. Very often this grass is planted at the beginning of the growing season, when the trees have a very minimal leaf canopy. Regardless, of when the grass is planted, initially the grass begins to recover from transplanting by growing new roots. All the while the trees are producing more and more leaves, reducing the amount of light reaching the grass. Suddenly, you notice the grass beginning to die back. The grass has reached the critical threshold of light where it can no longer produce enough energy to support itself. In order to survive, the grass begins to die back to keep in balance with the amount of energy that can be produced with the light available. This die back and thinning is normal and there is no chemical treatment that will help.

To improve the condition of your grass you must increase the amount of sunlight reaching it. This is accomplished by thinning out your trees, eliminating some of the trees, or selectively removing entire limbs. Reducing the overall leaf canopy by 25% to 50% is needed. DO NOT trim back the ends of the limbs, as this will encourage more leaf development reducing the amount of light reaching the grass.

GRASS IN THE SHADE

While St. Augustine sod is the most shade tolerant grass type available in Florida it will not grow under shady conditions as well as if it were in full sun.

All commercially grown sod, even the shade tolerant varieties are produced in the full sun. As a result, new sod will always go through a transition period while it adjusts to the reduced light in your yard. This transition period can last up to a year.

New grass planted under deciduous trees (like Oaks that drop all or part of their leaves in the winter) have particular difficulty during this transition period. Very often this grass is planted at the beginning of the growing season, when the trees have a very minimal leaf canopy. Initially the grass begins to recover from transplanting by growing new roots. All the while the trees are producing more and more leaves, reducing the amount of light reaching the grass. Suddenly, you notice the grass beginning to die back. The grass has reached the critical threshold of the amount of light where it can no longer produce enough energy to support itself. In order to survive, the grass begins to die back to keep in balance with the amount of energy that can be produced with the light available. This die back and thinning is normal and there is no chemical treatment that will help. Fertilizer will not replace sunlight.

To improve the condition of your grass you must increase the amount of sunlight reaching it. This is accomplished by thinning out your trees, eliminating some of the trees, or selectively removing entire limbs. Reducing the overall leaf canopy by 25% to 50% is needed. DO NOT trim back the ends of the limbs, as this will encourage more leaf development reducing the total amount of light reaching the grass.

Core aeration can help, but the real issue is sunlight. Please see Core Aeration and Establishing St Augustine in the Shade.

FERTILIZATION

Proper fertilization of any lawn grass is an important component of the best management practices of your home lawn. Fertilization and other cultural practices influence the overall health of your lawn, and can reduce or increase its vulnerability to numerous stresses, including weeds, insects, and disease.

It is advisable for homeowners to have soil tests done annually. Your local Cooperative Extension office has instructions and supplies for taking soil samples and submitting to the Extension Soil Testing Lab for analysis. In particular, phosphorous levels are best determined by soil testing. Since many Florida soils are high in phosphorous, little or no phosphorous may be needed for satisfactory lawn growth.

The grass growing in the shade should receive lower rates of fertilizer than that growing in full sun. Fertilizer should be applied to St. Augustine grass in 2 to 6 application from spring greenup through fall. Do not apply nitrogen too early in the growing season.. Likewise, don't fertilize too late in the year, as this can slow regrowth the following spring. If applying water-soluble forms at the lower application rate, it will take more applications to apply the total amount of fertilizer needed for the year than if applying a slow-release form.

For more information go to: http://edis.ifas.ufl.edu/LH010
St. Augustine grass for Florida Lawns. L.E. Trenholm, J.L. Cisar, and J. Bryan Unruh Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: May 1991. Revised: October 2000.

IRRIGATION

The best way to irrigate an established lawn is on an as-needed basis. Grass blades will begin to wilt (e.g., fold, turn bluish-green in color and not recover from traffic or footprints) as the moisture begins to be depleted in the soil.

If 30 to 50% of the lawn shows signs of slight wilting, it is time to irrigate with ¾ - 1" of water. The turf will fully recover within 24 hours. The turf should not be watered again until it shows signs of wilting. This irrigation schedule works for any soil type and environmental condition.

Proper watering practices will help maintain a lawn that requires less mowing and has little thatch buildup. Proper watering will also help develop a deep root system and be less susceptible to damage by pest and environmental stresses. If the diseases brown patch or gray leaf spot are a continuous problem, excessive watering and nitrogen fertilization may be responsible. Certain weeds (like pennywort and nutsedge) also thrive in soils which are continuously wet. Regulate these management practices closely to reduce disease and weed severity.

Irrigation on an as-needed basis is an efficient way to water any grass, providing that the proper amount of water is applied when needed. Normally, fall through spring is the driest period of the year. Therefore, irrigation is required to replace water lost via evapotranspiration. Apply enough water to rewet the soil rootzone and then wait until the turf shows signs of drought (e.g., wilting) again before the next irrigation (usually every 7 to 14 days in winter, 3 to 4 days in April-May, depending on soil type and maintenance practices).

For most Florida soils, no more than ¾ inch of water is necessary to rewet the upper 8 to 12 inches of the soil profile, which is where the majority of the roots are. To determine rates from a sprinkler system, place several coffee cans throughout the irrigation zones to find out how long it takes to apply ¾ inch of water. Irrigation is needed when leaf blades begin to fold up, to actually wilt, turn blue-gray in color, or when footprints remain visible on the grass. The length of the irrigation period to apply this ¾ inch can stay constant year round; only the frequency between irrigations should change.

Therefore, irrigation programs set by automatic timers do not need to operate on a daily schedule. They need only to operate after the turf begins to show signs of drought and then be programmed to apply an average of ¾ inch of water. Overwatering encourages nutrient leaching, increased pest problems, shallow rooting, and, of course, water waste.

For more information go to: http://edis.ifas.ufl.edu/LH010
St. Augustine grass for Florida Lawns. L.E. Trenholm, J.L. Cisar, and J. Bryan Unruh Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: May 1991. Revised: October 2000.

 

MOWING

Proper mowing practices are necessary to keep any lawn healthy and attractive. Under high levels of management, St. Augustine grass can be maintained at 2 inches if the lawn is mowed at least weekly during the growing season. Mowing at this height and frequency requires more fertilizer and water to maintain an attractive lawn. Also, low cutting heights and high maintenance levels can predispose the turf to many pest problems.

Under moderate or low levels of management, St. Augustine grass should be cut at a height of 3 to 4 inches. To obtain this height with most home rotary lawn mowers, the highest wheel height setting should be used. This height will help the grass develop a deep root system and give a better appearance to the turf. Mowing frequency under moderate or low management should be adjusted to the amount of growth. No more than one-third of the leaf blades should be removed with any mowing.

Low mowing heights can cause problems in turf quality. Repetitive low mowing reduces the density and vigor of St. Augustine grass and can lead to weed problems. The mowing height should be increased to 4 inches during periods of moisture stress or if the grass is growing in shade. Newer semi-dwarf varieties have a lower growth habit, and should be mowed at 1½ to 2 inches for optimum quality. Mowing too infrequently and watering improperly can cause a thatch buildup. The chapter entitled "Thatch and its Control in Florida Lawns" in this publication has more information on thatch.

Either a rotary or reel mower can be used on St. Augustine grass . It is important to keep the blades sharp and well-adjusted to get a clean cut. Dull blades will give the lawn a brownish cast, because a ragged cut shreds the leaf blades rather than cutting them. During the growing season blades should be sharpened on a monthly basis.
Grass clippings can be left on a lawn that is mowed at the proper height and frequency. Under these conditions, clippings do not contribute to the thatch layer. Clippings should be left on lawns maintained with low to moderate fertility levels to help recycle nutrients. If clippings are excessive (e.g., clumping occurs), let them dry out and then disperse them.

For more information go to: http://edis.ifas.ufl.edu/LH010
St. Augustine grass for Florida Lawns. L.E. Trenholm, J.L. Cisar, and J. Bryan Unruh Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: May 1991. Revised: October 2000.

 

PEST CONTROL

The best approach to weed control is a healthy, vigorous lawn. Weed problems in a lawn indicate that the turf has been weakened by improper management practices or damage from pests. Proper management practices can eliminate most weed problems. If weeds are a persistent problem, herbicides labelled specifically for St. Augustine grass should be used. Timing is critical for successful control.

The major pest of St. Augustine grass is chinch bugs . Check for chinch bugs by removing the ends of a coffee can, inserting one end through the soil at the margin of suspected damaged areas and fill with water. Chinch bugs will float to the water surface within 5 minutes. In areas where chinch bugs are a serious problem, a single thorough insecticide treatment may offer only temporary control. Other insect pests, including webworms , armyworms, grass loopers, and mole crickets

Mole crickets damage turfgrass areas primarily by the tunnels or soft mounds they leave while searching for food. Additional damage may result from small animals digging through the soil profile in search of the mole crickets as food. Check for mole crickets by: 1) examining an area for the tunnels, or 2) applying 2 gallons of water with 1½ ounces of detergent soap per 2 square feet in suspected damaged areas. Mole crickets will surface in several minutes. High levels of nitrogen fertilizer encourage insect problems.

Brown patch and gray leaf spot are the two major disease problems of St. Augustine grass . Brown patch occurs in warm, humid weather and is encouraged by excessive nitrogen. Gray leaf spot occurs during the summer rainy season and is primarily a problem on new growth. Both diseases can be controlled with fungicides.

Several types of nematodes infest St. Augustine grass lawns. Population peaks of nematodes typically occur in late April to early May and again in late August to early September. Damage symptoms include thin stand density, less vigorous growth, a weakened root system, slow recovery following rain or irrigation application, and certain weed invasion (e.g., prostrate spurge and Florida pusley). Soil nematode levels can only be positively identified through laboratory procedures. Inquire with your local county Cooperative Extension Service office on proper sample submission to the University of Florida Nematode Assay Laboratory.

For more information go to: http://edis.ifas.ufl.edu/LH010
St. Augustine grass for Florida Lawns. L.E. Trenholm, J.L. Cisar, and J. Bryan Unruh Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First published: May 1991. Revised: October 2000.