St. Augustinegrass is a warm-season grass growing in tropical and subtropical regions of the world. It is native to the Gulf Coast of North America, where it is a popular turf grass. It is also the most widely planted lawn grass in Florida. St. Augustinegrass, like most turf grasses, requires regular fertilization to keep it green and thick.
St. Augustinegrass is fast growing and thick. Regular precipitation and irrigation wash nutrients out of the soil, causing nutrient depletion. To keep up with nutritional needs, you will need to replenish soil nutrients. Proper fertilization helps strengthen St. Augustinegrass against threats such as weed and insect invasion, and disease.
Malnourished St. Augustinegrass displays reduced vigor, weak color and thinning turf. Growth slows down and invasive weeds begin to take over. Bare patches from insect damage are a sign of under-fertilization.
Turf grass fertilizers generally contain large amounts of nitrogen (N), low amounts of phosphorus (P), and an amount of potassium (K) about equal to nitrogen. N-P-K ratios, therefore, are something like 15-0-15 or 15-2-15. Each number represents the percent of each element in the formula. Nitrogen and potassium help with green growth and root production, respectively. It is preferable if part of the nitrogen content is slow-released, so it doesn't wash out too quickly with watering.
Fertilize St. Augustinegrass in two to six applications from spring through fall. Don't apply at the beginning or end of the season when there is danger of frost, which damages tender new growth. The more slow-release nitrogen your fertilizer has, the fewer applications will be needed over the season. Apply no more than 3 lbs. of nitrogen per 1,000 square feet of lawn per year. Water thoroughly after each application.
Excessive growth from over-fertilization causes thatch in St. Augustinegrass, making it susceptible to insect and disease problems. Pay attention to soil pH and don't add lime unless a soil test indicates its need. The analysis can also indicate if greater amounts of phosphorus are needed in your fertilizer formula.