Management of St. Augustine Lawns

Loss of St. Augustine grass in lawns throughout Texas is observed during the summer and fall months every year, those problems usually continue in the spring. While other turfgrasses are affected, St. Augustine grass lawns always seem to be hit the hardest.  Especially, this year we are seeing lawns affected by the drought coupled with freezing temperatures.  Most lawns did not have enough soil moisture during the freezing temperatures we experienced that left the root zones exposed to freeze damage.

            One of the problems I encounter in St. Augustine lawns each spring is yellowing or chlorasis. At first it appears to be an iron deficiency, but applications of iron don’t always correct the problem. The chlorosis may be due to a combination of factors, including lack of iron and nitrogen and St. Augustine Decline (SAD). SAD is caused by a virus that produces a chlorotic mottling affect that is often mistaken for iron chlorosis. I have come to the conclusion that most St. Augustine grass lawns are going to have some yellowing almost every year.

            Using best management practices for maintenance of St. Augustine grass lawns is one of the best things a homeowner can do to prevent stress to the lawn. Remember, many of the problems associated with the loss of St. Augustine turf are due to stress. While we can’t control the weather, managing the St. Augustine lawn properly will help reduce plant loss during periods of weather related stress. St. Augustine grass water requirements can be higher than other varieties of grass. Homeowners should evaluate the way they water their lawns.  Deep watering less frequent watering will allow grasses to develop deeper and healthier root systems.

            Fertilization is always key to maintaining healthy landscapes.  The recommended rate of nitrogen for St. Augustine grass growing in full sum is 3-4 pounds of actual N per 1000 square feet per year.  For shade areas, the recommended rate is 1-2 pounds of actual N per 1000 square feet per year. Rates of phosphorous and potassium should be determined by a soil test.

            Apply the first application after the lawn has been mowed a couple of times in the spring. Then for a St. Augustine grass growing in full sun, fertilized once in the summer and again in the fall. Shady areas should be fertilized once in the spring and once in the fall for best results.

            Another common problem in St. Augustine lawns is brown patch. Normally this disease shows up in the fall. However, this disease has been reported in St Augustine grass lawns throughout Texas in the spring each year. There are several fungicides available locally that are labeled for brown patch control. While brown patch doesn’t normally kill affected plants, it can weaken the affected area and make them more susceptible to other stress problems such as freezing temperatures or drought. Close observation of the affected area reveals leaves with a rotted sheath, which means the leaf can easily be pulled from the stolon.

            Take All Root Rot (TARR) can also be a major contributor to problems in St. Augustine lawns. This fungus attacks the root system primarily in the fall and spring months when soil temps are in the 60-65 degree range. Any factor that causes stress to the turf will enhance the potential for TARR to become a problem. TARR is characterized by brown leaf blades that are firmly attached, brown stolons and a shortened root system that is brown to black in color. Control can be difficult. Approved fungicides may help. Topdressing the affected areas with sphagnum peat moss has also provided some control. Peat moss must be watered in thoroughly to be effective.

            New homeowners looking to establish a home lawn needs to select a grass that will be suited to the growing conditions in north Texas.