How to Fertilize St. Augustine Grass | The Simple Schedule

Fertilizing St. Augustine grass correctly means applying 2–4 pounds of nitrogen per 1,000 square feet each year, split into 3–4 feedings from spring through early fall using a slow-release granular fertilizer.

Getting the feeding right for St. Augustine grass is about timing, amounts, and the right nutrient balance — not dumping a bag on the lawn and hoping it works. One wrong application during dormancy can damage the turf, but a well-planned schedule keeps it dense, dark green, and resistant to disease. The table below breaks down the four key feedings for a healthy lawn, followed by the exact steps to apply them.

The Four-Feeding Schedule for St. Augustine

St. Augustine needs nitrogen spread across the growing season, not all at once. Apply only when the grass is fully green and actively growing — never to dormant grass between November and February. Each round uses a different fertilizer ratio to match what the grass needs at that stage of the season.

For most regions, stop fertilizing after mid-October. In northern areas with earlier frost, stop by mid-September. Dormant grass cannot use the nitrogen — it simply feeds weeds and wastes your money.

How Much Fertilizer to Apply Each Time

Each application should deliver 0.5–1.0 pound of actual nitrogen per 1,000 square feet. To figure out how many pounds of bagged fertilizer that means, divide 100 by the first number on the bag (the nitrogen percentage). For a 16-4-8 bag: 100 ÷ 16 = 6.25 pounds of fertilizer per 1,000 square feet. For a 15-0-15 bag: 100 ÷ 15 = roughly 6.7 pounds. Always set your spreader to deliver that amount evenly across the lawn.

An annual total of 2–4 pounds of nitrogen per 1,000 square feet is the standard range. Warmer climates with longer growing seasons may push toward the higher end; cooler regions stay near the lower end. If you want a bulletproof starting point, use 15-0-15 for most feedings — it provides nitrogen and potassium without adding phosphorus, which many soils already have in adequate amounts.

Applying Fertilizer the Right Way

The steps are simple but skipping any one causes uneven results. Run through this sequence for every feeding:

1. Soil test first: Check pH (ideal range is 5.5–6.5) and phosphorus levels before choosing a fertilizer blend.
2. Timing: Wait until three weeks after the grass has turned fully green and all frost risk has passed.
3. Prep the lawn: If the soil is dry, water the day before to help the granules break down.
4. Broadcast evenly: Use a spreader to apply the calculated amount, overlapping slightly to avoid stripes.
5. Water it in: Run the sprinklers immediately after application to wash the granules off the blades and into the soil.
6. Watch and adjust: Monitor for signs of deficiency (yellowing) or excess (burn tips, rapid thatch buildup) and shift the schedule accordingly.

If you are shopping for a product to use for the mid-summer or early-spring feeding, our tested roundup of summer fertilizers for St. Augustine compares the top slow-release blends that work well during those hotter months.

Common Mistakes That Hurt St. Augustine

Most lawn issues with St. Augustine come from timing errors or bad ratios, not a lack of effort. Three problems show up more often than the rest:

• Fertilizing dormant grass: Applying nitrogen before the grass is fully green or after it has browned for winter wastes the product and feeds winter weeds.
• Heavy nitrogen in fall: Nitrogen pushes tender new growth that dies back in the first cold snap. Always switch to a low-nitrogen, high-potassium formula for the final fall feeding.
• Big doses spread far apart: One heavy feeding every three months is less effective than lighter applications every 6–8 weeks. Frequent, small feedings produce steady growth and less risk of burn.