St. Augustine or Charleston Grass is a popular warm-season grass grown in residential and commercial areas in southern United States. It is planted by sprigs, plugs or sod, and if maintained properly it chokes out most weeds naturally, eliminating the use of herbicides. A timely fertilizer schedule is essential to ensure grass health and reduce its vulnerability to pests and diseases.
St. Augustine Lawn Types
There are generally two types of St. Augustine lawns, and fertilizer for each varies accordingly. Feed newly planted lawns a well-balanced or high phosphorus starter fertilizer on a monthly basis at the time of planting and for up to three months afterwards. Feed an established St. Augustine lawn a nitrogen-rich fertilizer so it retains its color and grows thick, lush and healthy.
A fertilizer has three essential elements: nitrogen, phosphorus and potassium (N-P-K). Nitrogen is essential to retain the green color; phosphorus improves root growth and increases the quality of crop and potassium or potash is essential for plant photosynthesis and protein and starch production.
Homeowners and gardeners should conduct a soil test in early spring to determine the percentage of nutrients present in the soil so they feed the grass the appropriate fertilizer. While the second two elements (P-K) are essential to a healthy St. Augustine lawn grass, it is imperative that fertilizer is applied to the rate of nitrogen. According to the Texas Cooperative Extension, most established lawns do not require high phosphorus in the form of fertilizer as they are high in plant-available phosphorus, but use up to 2 percent if the soil test indicates additional need. Use fertilizers with half as much potassium as nitrogen to increase cold- and drought-tolerance of newly planted and established St. Augustine grasses.
Feed established grass on sandy soils one pound of fertilizer for every 1,000 square feet of area. Over-fertilizing makes the grass lush but susceptible to pests and diseases.
Fertilize the St. Augustine lawn grass in late fall or early spring, when it is still brownish-yellow and starting to grow. Spread one pound of nitrogen fertilizer over the area with a spreader, and continue to do so every 30 to 60 days until late fall. This extends the time when the lawn is most attractive.
Fertilize the St. Augustine grass two to six times from spring green-up to fall. Provide more applications of water soluble fertilizers that were applied at a lower rate to equal the amount of fertilizer needed for the year as compared to a slow release one.
Use a spreader that ensures an even distribution of fertilizer. Fill it in the driveway and not over the grass to prevent overfeeding in the event of any spills.