Lawn Care · Fertilizer
St. Augustine wants moderate nitrogen, and none of it early.
Most extension programs feed St. Augustine 2 to 4 lb of nitrogen per 1,000 sq ft a year (more in South Florida, about half that in shade), in ½ to 1 lb doses that start only after the lawn is fully green. The best bag is high in nitrogen, low or zero in phosphorus, carries a real share of slow-release nitrogen and, in much of Florida, meets your county’s fertilizer ordinance.
YEARLY N, SUN
2–4 lb per 1,000 sq ft
YEARLY N, SHADE
1–2 lb
PER FEEDING
½–1 lb N
FIRST FEEDING
After full green-up
How much nitrogen St. Augustine needs
St. Augustine is a medium feeder. It needs less than hybrid Bermuda and more than centipede, and the Southern extension programs land in a similar range. Figures are pounds of actual nitrogen per 1,000 sq ft per year.
| Program | Yearly N | How it’s split |
|---|---|---|
| Clemson HGIC 1218 (South Carolina) | 2–4 lb (high end on sand) | ½–1 lb in early May, June–July and before Aug 15. On Piedmont clay, only twice. |
| UF/IFAS ENH5 (Florida) | North 2–4; Central 2–5; South 4–6 | 2–6 feedings from green-up through fall; year-round in South Florida |
| Texas A&M E-436 | Sun: 2 / 2–3 / 3–4 (low, moderate, high care). Shade: 1 / 1–2 | Feedings of 1 lb or less, at least 45–60 days apart |
| LSU AgCenter (Louisiana) | 2, or 3 for more growth | 1 lb in April and June, optional 1 lb in August |
Two things push the number down: shade and disease history. Texas A&M roughly halves the rate for shaded St. Augustine, and UF says too much water and nitrogen contribute to large patch and gray leaf spot. If your lawn has had either, aim for the low end.
Match the fertilizer to your situation
| Your situation | What to look for | Why |
|---|---|---|
| Soil test says phosphorus is adequate | High-N, zero-P (for example 32-0-10 or 34-0-10) | Clemson: apply phosphorus only when a soil test recommends it. |
| No soil test | About 4 : 1 : 2 N-P-K (for example 16-4-8), then get a test | Texas A&M suggests 4–6 : 1 : 2–4 without a recent test. |
| Florida county with a fertilizer ordinance | At least 50% slow-release N, 0% P unless a soil test shows a need; nothing with N or P during the summer ban | Many Florida ordinances bar N and P from about June 1 to Sept 30 (UF/IFAS Lee County); St. Lucie adds the 50% slow-release and 0% P rule (UF/IFAS). |
| Shady lawn | Fewer, lighter feedings | Texas A&M: 1–2 lb a year in shade. Mow 3–4 inches there (Clemson). |
| Yellow in summer on alkaline soil or well water | Iron (ferrous sulfate or chelated iron), not extra nitrogen | UF says iron greens the lawn but doesn’t fix nitrogen-deficiency yellowing. |
| Late summer, before winter | Potassium if the soil test is low to medium | Clemson: about 1 lb K2O per 1,000 sq ft, 4–6 weeks before first frost. |
| Broadleaf weeds plus feeding | Weed and feed labeled for St. Augustine, only if you have the weeds | Label limits apply; see the products table and the warning below. |
St. Augustine fertilizer products compared by label
We haven’t run trials of these products. This compares their labels with the extension targets above. Labels were checked in October 2026; re-check the bag, especially for the slow-release percentage, which some product pages don’t publish.
| Product | Analysis | At the label rate | Slow-release N | Fit for St. Augustine |
|---|---|---|---|---|
| Scotts Turf Builder Southern Lawn Food | 34-0-10 | About 1.2 lb N per 1,000 sq ft (28.24 lb per 8,000 sq ft); 1.6 lb at the “Max Greening” rate | Not stated on the product page | Right nutrient shape, but the label dose is heavier than the ½–1 lb most programs use. About 2.9 lb per 1,000 sq ft gives 1 lb N. |
| Scotts Turf Builder Southern Lawn Food FL | 32-0-10 | 14.06 lb per 5,000 sq ft = about 0.9 lb N per 1,000 sq ft | Not stated on the product page | Florida version. Label says one application a year, none in winter in North Florida and none within a month of first frost. |
| The Andersons Professional 16-4-8 with NS-54 | 16-4-8, 2% iron | 6.25 lb per 1,000 sq ft = 1.0 lb N | About 40% (6.4 of 16 points) | Good no-soil-test choice outside Florida. Below the 50% slow-release minimum and not 0% P, so it doesn’t meet St. Lucie-style ordinances. |
| Milorganite | 6-4-0, 2.5% iron | 32 lb per 2,500 sq ft = about 0.77 lb N | About 58% | Gentle and iron-rich, but the phosphate keeps it out of 0%-P ordinance counties unless a soil test shows a need. See how to use Milorganite. |
| Scotts Turf Builder Bonus S Southern Weed & Feed | 29-0-10 + atrazine | Bag covers up to 10,000 sq ft | Not stated | Labeled for St. Augustine (Floratam included), centipede, zoysia and carpetgrass. At least 2 months between applications; keep it off flowers and shrubs. |
Worked example: Central Florida Floratam under an ordinance
Take a 5,000 sq ft Floratam lawn in a county with a June 1–Sept 30 ban, a 50% slow-release minimum and a 0% phosphorus rule. UF’s Central Florida range is 2–5 lb a year, and the first feeding there is early April. A 3 lb plan looks like this:
- Early April: 1 lb N per 1,000 sq ft, after full green-up.
- Mid-May: 1 lb N, before the ban starts.
- June–September: no N or P. If you want color, a product with no nitrogen or phosphorus (often sold as a “summer blend”) is what the ordinances leave open.
- October: 1 lb N, while the grass is still growing.
For each 1 lb feeding you need a 0-P bag that states at least 50% slow-release nitrogen. That also keeps the quick-release part at ½ lb, under UF’s 0.7 lb per-application cap. With a 30-0-x product, that’s about 3.3 lb per 1,000 sq ft, or roughly 17 lb per feeding for the whole lawn. Every county writes its own rules, so check yours before buying.
In Texas the same logic runs on frost dates. E-436 puts the first feeding about 6 weeks after your average last frost and the last one by Oct 15 in Austin, Houston, San Antonio and Waco, or Oct 1 in Dallas.
Don’t feed St. Augustine before it has fully greened up.
An early-spring push is the mistake to avoid. LSU AgCenter warns that nitrogen applied too early encourages weeds and large patch, and LSU notes St. Augustine is more prone to large patch than some other turfgrasses. In North Florida, UF adds that late frosts can damage grass pushed out too soon. Clemson’s calendar puts no nitrogen down from January through April.
Weed and feed has its own timing trap. Clemson says not to apply weed killers to St. Augustine while it’s greening up or when it’s 90°F or hotter, and notes the grass is sensitive to 2,4-D, which is in many three-way mixes. If you only have a few weeds, spot-treat them and feed with plain fertilizer.
If you’d rather not track ordinances and rates yourself, our lawn fertilization page connects you with a lawn care company serving your area.
St. Augustine fertilizer FAQs
Is 15-0-15 good for St. Augustine?
Yes, for summer. Clemson names a high-potassium product like 15-0-15 for its June–July and August feedings. At 1 lb N it takes about 6.7 lb per 1,000 sq ft.
How often should I fertilize St. Augustine?
Two to four times a year for most lawns, 6–8 weeks or more apart, from full green-up to late summer. South Florida lawns can be fed year-round under UF guidance, subject to local ordinances.
Does St. Augustine need iron?
Often, on alkaline soils. Clemson suggests 2 oz of ferrous sulfate in 3–5 gallons of water per 1,000 sq ft in summer to improve color without pushing growth. Iron won’t fix a nitrogen shortage, though. See iron for lawns.
Can I use weed and feed on St. Augustine?
Yes, if the label lists St. Augustine. Atrazine-based Southern weed and feed is labeled for it. Use it only when weeds are actually present, follow the spacing on the label, and keep it off beds.
Does St. Augustine need phosphorus?
Only when a soil test shows it’s low. Clemson applies phosphorus by soil test only, and many Florida ordinances require 0% phosphorus unless a test shows a deficiency.
What should I feed St. Augustine in the fall?
Potassium if your soil test is low, applied 4–6 weeks before first frost. Outside Florida, skip fall nitrogen: Clemson puts none down from September through December. Florida lawns can take a fall feeding while still growing, per UF.
Related guides
FERTILIZER
Best fertilizer for Bermuda grass
Nitrogen targets and timing for the hungrier warm-season grass.
Sources: Clemson HGIC 1218: St. Augustinegrass Yearly Maintenance · UF/IFAS ENH5: St. Augustinegrass for Florida Lawns · Texas A&M E-436: Fertilizing Texas Lawns · LSU AgCenter: Taking Care of St. Augustinegrass Lawns · LSU AgCenter: April lawn fertilizing · UF/IFAS Extension: St. Lucie County fertilizer ban · UF/IFAS Extension: Lee County fertilizer product survey · Scotts Turf Builder Southern Lawn Food · Scotts Turf Builder Southern Lawn Food FL · Scotts Bonus S Southern Weed & Feed · The Andersons 16-4-8 label · Milorganite specifications
