Sorting the Cultivars
Your guide to the newest varieties of St. Augustine for Texas

St. Augustinegrass is a popular choice for lawns in much of inland Texas, as well as across Coastal Texas, where temperatures are moderated by the Gulf of Mexico. St. Augustinegrass is a tropical grass that adapts to sub-tropical climates. There are many St. Augustinegrass varieties and cultivars to draw from. This discussion will revolve around the most reliable types to choose for your particular situation.

North Central Texas is at the northern limit for growing St. Augustinegrass successfully. Some winters in North Texas, the temperature may fall into or below the 16 F to 20 F range, where freeze damage can adversely affect St. Augustinegrass lawns. This past winter season in North Texas was a good example; temperatures dipped into the upper teens and for an extended period – almost 72 hours – stayed below freezing. This stress resulted in areas of death in some St. Augustinegrass lawns, or compromised them to a point where they were more susceptible to damage by the take-all root rot (TARR) pathogen, which was very active this past spring.

(Please note, for this discussion, that all types of St. Augustinegrass are susceptible to TARR and white grub damage. There is no evidence of resistance among the different varieties of St. Augustinegrass to these pests, so even though they are of concern, it is not necessary to include them in the comparative lists below.)

North of Austin
First, let’s address the varieties of St. Augustinegrass best suited for lawns north of Austin. Raleigh St. Augustine has replaced common St. Augustine as the measure by which we examine the characteristics of new introductions of St. Augustinegrass in Central and North Texas. (This replacement occurred in the ‘80s due to Raleigh’s resistance to the St. Augustine decline virus, SADV, which was decimating common St. Augustine.) Here is the comparison of traits for several types of St. Augustinegrass, based on research trials and accompanying claims by sod distributors and producers:

Raleigh
    •    Medium green color, medium texture
    •    Good cold tolerance
    •    Above-average drought tolerance
    •    Vigorous; establishes well
    •    Adapts to most soils
    •    Susceptible to brown patch (BP), chinch bugs (CB) and gray leafs (GLS)
    •    Resistant to St. Augustine decline virus (SADV)

DelMar
    •    Dark green color, medium texture
    •    Slightly more cold  tolerance
    •    Slightly better shade and drought tolerance
    •    More susceptible to BP
    •    Susceptible to CB and GLS
    •    Resistant to SADV

Palmetto
    •    Deep green color, medium texture
    •    Better cold tolerance
    •    Improved drought tolerance
    •    Similar shade tolerance
    •    Susceptible to BP and GLS
    •    Has shown some resistance to CB
    •    Debate ongoing for resistance or susceptibility to SADV

Seville
    •    Medium green color, medium texture
    •    Less cold tolerance
    •    Similar shade tolerance
    •    Susceptible to BP, CB and GLS
    •    Resistant to SADV

South of Austin/San Antonio
To address the grasses suited to areas south of Austin/San Antonio and to the immediate Gulf Coast, comparisons are made to Floratam St. Augustine, the dominant St. Augustinegrass for the area. The varieties for Coastal and South Texas include:

Floratam
    •    Blue-green color, coarse texture
    •    Rapidly growing grass
    •    Purple stolons (stems)
    •    Resistant to SADV and CB in Texas
    •    Less susceptible to BP and GLS
    •    Excellent drought tolerance
    •    Very poor cold tolerance

Amerishade
    •    Deep green color, medium texture
    •    Slow vertical growth tends to develop thatch
    •    Good to excellent shade tolerance
    •    Good cold tolerance
    •    Susceptible to BP, CB and GLS
    •    Resistant to SADV

Sapphire
    •    Dark green color, coarse to medium texture
    •    Purple stolons, rapid growth
    •    Recovers well from wear
    •    Reduced weed problems
    •    Fair to good drought tolerance
    •    Jury is still out on cold tolerance, as well as pest and disease resistance or
         susceptibility compared to Floratam.

St. Augustinegrasses perform in a wide range of sites, preferring full sun but  tolerating and adapting to shade conditions. Use this information to consider your options. Whether you choose an industry standard such as Floratam in the south, Raleigh in the north or take a chance on the newer types, it is important to recognize their positive and negative traits to assist in making the most suitable choice for your lawn.

About the author: Mike Sutton is a horticulture graduate of Purdue University  with more than 25 years’ experience with turf grasses in Texas.