The most shade tolerant warm-season grass, St. Augustine grass (Stenotaphrum secundatum) is rarely propagated from seed. Most varieties are sterile, and seeds from the few fertile varieties are not often available. St. Augustine grass is hardy in U.S. Department of Agriculture plant hardiness zones 8 through 10, with some cold-tolerant strains hardy to USDA zone 7.
The strains of St. Augustine grass grown in Florida are generally an infertile variety. These varieties have purple-colored stigmas, which are the female parts of a flower. The strains grown in Texas are fertile and have white-colored stigmas. "Texas Common" is one of the more cold-hardy types of St. Augustine grass that can survive cooler winters and is hardy in USDA zones 7 through 10. Though some varieties produce viable seed, the seed is rarely available for purchase, either online or locally.
If seed can be located for fertile varieties of St. Augustine grass, it is established by planting 1/3 to 1/2 pound of seed per 1,000 square feet. Calculate the total amount of seed required, and then spread half in a left to right direction across the lawn and half in the opposite direction, working back to front. Rake the soil lightly to cover seed and press it into the soil. The best time to seed is late spring or early summer. Soil moisture is essential for grass to germinate, and the soil should be kept moist for several weeks until the seedlings begin to emerge.
Alternate Planting Methods
Most St. Augustine grass is propagated vegetatively by planting plugs, sod or sprigs. These establish more quickly than seeded lawns and are a more reliable way to propagate St. Augustine grass. Sod is the fastest way to establish a new lawn, since it covers the entire surface of the lawn with grass plants. Plugs planted 1 to 2 feet apart in the spring can cover the lawn area in one growing season. St. Augustine grass can also be established by planting sprigs in rows 6 to 12 inches apart by hand or using a mechanical sprigging machine.
After Planting Care
Keeping the lawn moist after planting is important for sprigs, plugs and sod as well as seed. On days without rain, water sprigs and plugs every day for the first two weeks. For sod, water twice a day. St. Augustine grass has high fertilizer needs. Apply a starter fertilizer high in phosphorus and work it into the top 2 to 4 inches of soil just before planting. Starter fertilizer with an N-P-K ratio of 10-25-12 is applied at a rate of 3.6 to 4 pounds per 1,000 square feet. Continue applying nitrogen once a month at a rate of 1 pound of nitrogen per 1,000 square feet to promote fast growth of plants and seedlings.