St. Augustine grass needs 2–4 feedings between spring green-up and early fall, applying 0.5–1 lb nitrogen per 1,000 sq ft each time for healthy growth.
St. Augustine grass thrives on a feeding schedule timed to its growth cycle, not the calendar. A solid St. Augustine grass fertilizer schedule calls for 2–4 applications during active growth—from spring green-up through early fall—with each feeding delivering 0.5 to 1 pound of actual nitrogen per 1,000 square feet. The exact timing, product, and rate depend on your region, soil type, and a soil test, but the core principles hold across warm-season lawns.
When Should You Start Fertilizing St. Augustine Grass?
Fertilize only after the lawn has fully greened up in spring and has been mowed at least twice. Feeding dormant grass wastes fertilizer, feeds winter weeds, and invites disease. In warmer coastal areas the first feeding may come by late April; in cooler inland regions it starts closer to late May or early June, once the grass is actively growing.
The last nitrogen application should land 4–6 weeks before the first expected frost, and no later than mid-September to mid-October regardless of region. After that, St. Augustine grass prepares for dormancy and should not receive nitrogen again until spring. A late-season potassium feeding instead of nitrogen helps the lawn handle cold stress.
Choosing the Right Fertilizer Blend
A 3-1-2 or 4-1-2 N-P-K ratio—such as 16-4-8, 15-5-10, or 12-4-8—works well for St. Augustine grass under typical soil conditions. But a soil test should guide your final choice. Add phosphorus (the middle number) only when the test recommends it; unnecessary phosphorus can run off into waterways. If phosphorus is already adequate, choose a low- or zero-phosphorus blend like 15-0-14 or 15-0-15.
For late-season feeding, switch to a higher-potassium blend such as 15-0-15 or a 0-0-4 style product to improve stress tolerance without adding more nitrogen. If the lawn looks yellow but the soil pH is high, the problem is often iron deficiency, not a lack of nitrogen—an iron supplement or chelated iron spray corrects the color without pushing excess growth. For a hands-on look at what works, check our recommended fertilizers for St. Augustine grass with tested product picks.
How Much Fertilizer Should You Apply Per Feeding?
Apply 0.5 to 1 pound of actual nitrogen per 1,000 square feet per feeding, and never exceed 1 pound in a single application. The total for the growing season should stay between 2 and 4 pounds of actual nitrogen per 1,000 square feet. Space feedings 6 to 8 weeks apart and use a slow-release or mixed-release product to reduce burn risk and surge growth.
| Application | Timing | Nitrogen per 1,000 sq ft |
|---|---|---|
| First | After green-up & 2 mowings | 0.5–1 lb |
| Second | 6–8 weeks after first | 0.5–1 lb |
| Third | 6–8 weeks after second | 0.5–1 lb |
| Fourth (optional) | Early fall, before mid-September | 0.5 lb |
| Fall potassium | 4–6 weeks before frost | Potassium blend, no N |
Water in the fertilizer per the product label, and sweep any granules off hard surfaces to keep them out of storm drains. On sandy soils, split the yearly total into more frequent, lighter feedings—four to five smaller doses—since nutrients leach quickly through sand. On clay soils, fewer heavier feedings work because clay holds nutrients longer.
Regional differences matter. In South Carolina’s Piedmont and Midlands clay areas, Clemson recommends fertilizing only twice during the growing season. North Carolina State’s schedule suggests ½ lb of nitrogen in May, ½ lb in June, 1 lb in July, and ½ lb in August. Texas A&M caps total nitrogen at 4 lb per 1,000 sq ft per year and advises combining quick- and slow-release sources, as outlined in their St. Augustinegrass management calendar. Florida guidance typically delays the first application until the lawn has been mowed twice and uses about 1 lb per 1,000 sq ft in spring. The common thread: fertilize only when actively growing and stop well before dormancy.
FAQs
Can I fertilize St. Augustine grass in winter?
No. St. Augustine grass goes dormant or slows significantly once soil temperatures drop below 60°F. Fertilizing during dormancy feeds winter weeds and encourages large patch disease without benefiting the turf. Wait until the lawn fully greens up in spring and has been mowed at least twice before applying any nitrogen.
What happens if I apply too much nitrogen?
Excess nitrogen produces rapid, weak growth that invites disease and thatch buildup, and it raises the risk of fertilizer burn. It also pushes the lawn above the recommended 4 lb of nitrogen per 1,000 sq ft per year, which can stress the turf long-term. Stick to 0.5–1 lb per feeding and use slow-release formulations.
Should I use a weed-and-feed product?
Use caution. Many weed-and-feed products contain herbicides like atrazine or 2,4-D that can damage St. Augustine grass if applied during spring green-up or when temperatures exceed 85°F. Apply fertilizer and weed control separately, using products specifically labeled safe for St. Augustine grass, and follow the label timing closely to avoid injury.
References & Sources
- Texas A&M AgriLife Extension. “St. Augustinegrass Management Calendar.” Nitrogen rate and timing guidance for Texas lawns.
- Clemson Cooperative Extension. “St. Augustinegrass Maintenance Calendar.” Regional schedule guidance for South Carolina.
- NC State Extension. “St. Augustinegrass Lawn Maintenance Calendar.” Month-by-month fertilizer and care recommendations for North Carolina.