St. Augustine grasses for Florida lawns

St Augustinegrass.JPG

St. Augustine grass (Stenotaphrum secundatum [Walt.] Kuntze.), is widely adapted to the warm, humid (subtropical) regions of the world. It is believed to be native to the coastal regions of both the Gulf of Mexico and the Mediterranean.

In Florida, St. Augustine grass is the most commonly planted turf grass in the urban, coastal areas. It performs best in well-drained, fertile soils but can grow satisfactorily in a wide variety of soils. To produce an acceptable quality lawn, St. Augustine grass requires irrigation and moderate fertility. 

Advantages

St. Augustine grass produces a green to blue-green dense turf that is well adapted to most soils and climatic regions in Florida. It has relatively good salt tolerance and certain cultivars possess good shade tolerance. Establishment of St. Augustine grass from sod is quick and easy. Several different cultivars of St. Augustine grass sod and plugs are available from garden centers and custom sod installers throughout Florida.

Disadvantages

St. Augustine grass, like most turf grasses, has certain cultural and pest problems. It does not remain green during drought conditions without supplemental irrigation. It produces excessive thatch under moderate to high fertility and frequent irrigation. It has poor wear tolerance and some varieties are susceptible to cold damage. The coarse leaf texture is objectionable to some people.

The major insect pest of St. Augustine grass is the chinch bug, although resistance to chinch bugs varies somewhat among cultivars. For example, Floratam and Floralawn have traditionally been considered chinch resistant, but over time the insect has overcome this and are now considered a pest to these cultivars as well.

St. Augustine Decline Virus (SADV) is a major disease problem in some parts of the United States but has not been identified as a problem in Florida. Some cultivars are also susceptible to gray leaf spot disease.

Cultivars

There are several cultivars of St. Augustine grass available for lawn use in Florida. The different cultivars vary in their tolerances to environmental stresses or their susceptibility to pests, so it is advisable to check with your county Cooperative Extension Service office for the best grass for your location and needs.

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 St. Augustine grass for Florida Lawns 3 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 web worm 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 web worms 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 1 1/2-2 1/2 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 web worms, and brown patch disease. These also have slow lateral runner growth, thus, require longer periods for grow-in from plugs or recovery from damage.

Maintenance of St. Augustine grass

It is advisable to check with your local County Extension office for cultivars best adapted to your geographical area and uses. As emphasized throughout the Florida Lawn Handbook, proper lawn maintenance practices are the best means for avoiding pest problems and obtaining a high quality lawn.

Establishment

The best time to establish St. Augustine grass is during the spring or early summer months. This enables the grass to grow in before cooler weather begins, when growth will be reduced. In south Florida, establish St. Augustine grass during winter or spring.

When establishing any grass, it is important to provide irrigation more frequently than normal recommendations call for. Frequent, short irrigations throughout the course of the day will help the root system to become established in the soil and viable.

Mowing should not be done until the roots have had a chance to peg down into the soil. Vegetative propagation means that plant parts with growing points are used for planting rather than seeds. St. Augustine grass has stolons (above ground stems) that have areas of actively dividing cells at the nodes. These areas are capable of generating new shoot growth and are responsible for lateral growth of St. Augustine grass along the ground.

Sodding

Sodding will produce an instant lawn, as you virtually cover the entire area to be planted with grass material. Sod should only be laid over bare moist soil with pieces laid in a staggered brick-like pattern and the edges fitted tightly together to avoid any open cracks. Rolling and watering thoroughly will insure good contact with the soil for fast rooting.

Sodded areas should be watered at least twice per day with 1/4 inch of water until the sod is held fast (usually 2 to 3 weeks) to the soil by roots; then watering should be reduced to an as-needed basis.

Sprigging

Sprigging is less expensive than sodding, but does not produce an instant lawn as does sodding. It is a labor-intensive way to cover a large area. Sprigs contain nodes on stolons, which are planted end-to-end in furrows 6 to 12 inches apart. Stolons should be covered with soil, but leaf blades should be left exposed. The soil should be tamped and watered in thoroughly. Soil should be kept moist until new stolons appear.

Plugging

A number of St. Augustine grass cultivars are available commercially as plugs. Sod also can be made into plugs by cutting it into small squares. Spacing of plugs varies from 6 to 24 inches. The closer spacing provides full coverage in 3-6 months and farther spacing covers in 6 to 12 months. Plugs are placed in holes of the same size or in open furrows and tamped into place. A thorough watering completes the installation. The turf should then be cared for like a sprigged lawn.

Fertilizing

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 St. Augustine grass for Florida Lawns 5 soils are high in phosphorous, little or no phosphorous may be needed for satisfactory lawn growth.

Maintaining a good quality lawn requires a properly planned fertility program. An acceptable quality St. Augustine grass lawn can be grown with a low to high level of fertility, depending on what the homeowner wants. First, decide how much time and effort can be spent on lawn maintenance.

A lower fertility lawn is best for those with little time to spend on lawn care. A high fertility lawn may be better suited to those who desire a manicured appearance for their yard. This type of maintenance will require more time and money for lawn care.

In general, two weeks following spring regrowth, apply a complete fertilizer such as 16-4-8 at the rate of 1/2 (water-soluble) to 1 (slow-release) pound of nitrogen per 1000 square feet. The three numbers refer to percent nitrogen, phosphorous, and potassium, respectively, in the bag.

For example, a 50-pound bag of 16-4-8 contains 16% nitrogen or 8 pounds total nitrogen. This bag will fertilize 8000 square feet at the rate of 1 pound of nitrogen per 1000 square feet at this rate. Higher fertilization rates will produce a faster buildup of thatch than lower rates. High rates of fertilizing can also encourage insect damage to the turf. Additionally, the necessary amount of mowing and watering increases with the amount of fertilizer.

University of Florida guidelines for lawn grass fertility show a range of fertilizer rates over which a particular species may be successfully grown for various areas of the state. These ranges are included to account for individual homeowner preferences for low-, medium-, or high-input grass. Additionally, localized microclimate effects can have a tremendous effect on turf grass growth, and a range of rates provides more opportunity to allow for these environmental variations.

An example of this would be a typical home lawn that is partially shaded and partially sunny. The grass growing in the shade should receive lower rates of fertilizer than that growing in full sun. The guidelines are also separated into three geographical locations statewide as indicated in Table 2 and Table 3 . All rates are in pounds of nitrogen per 1000 square feet. For questions on how to apply these amounts, refer to the section in this book entitled Florida Fertilization.

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, particularly in north Florida, or subsequent frosts may damage the grass. 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.

On high pH (>7.0) soils or where high pH water is applied, yellow appearance may be an indication of iron or manganese deficiency. For iron deficiency, spray ferrous sulfate (2 ounces in 3 to 5 gallons of water per 1000 square feet) or a chelated iron source (refer to the label for rates), to temporarily enhance color. Iron applications every 6 weeks will help maintain green color and, unlike nitrogen, will not promote excessive top growth.

Lower the soil pH by applying 15 pounds of elemental sulfur per 1000 square feet prior to grass establishment. Once the grass is established, up to 5 pounds of elemental sulfur may be added per 1000 square feet, it if is immediately irrigated in to prevent burn.

Using ammonium nitrate or sulfate as a fertilizer source will also help to temporarily reduce soil pH. Apply manganese as a fertilizer with micro-nutrients or as straight manganese sulfate (MnSO4) bimonthly at 0.41 pounds per 1000 square feet (18 pounds per acre) to relieve deficiency symptoms if present.

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. 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 1 1/2 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.

Watering

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 3/4 - 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. For further information on recommended watering practices see the chapter in this publication entitled "Watering Your Florida Lawn."

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 evapo-transpiration.

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 3/4 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 3/4 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 3/4 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 3/4 inch of water. Over watering encourages nutrient leaching, increased pest problems, shallow rooting, and, of course, water waste.

Information provided by the University of Florida's IFAS Extension