How to Fertilize St. Augustine Grass

Stenotaphrum secundatum

Reviewed by Kiersten Rankel M.S.

Quick Answer

Use a high-nitrogen fertilizer with a ratio like 15-0-15 or 16-4-8 that includes iron. Apply every 6 to 8 weeks from late spring through early fall. Do not fertilize dormant grass in winter.

When Should I Start Feeding My St. Augustine Grass?

Begin fertilizing after the grass exits dormancy and is actively growing, which depends heavily on your region since St. Augustine grows in zones 8a through 11b.

Pacific Mar–Oct

Mountain Jun–Aug

Midwest May–Sep

Northeast Jun–Aug

Southeast Apr–Oct

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How Often Should I Fertilize My St. Augustine Grass?

Apply fertilizer every 6 to 8 weeks during the active growing season. St. Augustine Grass needs 2 to 4 pounds of nitrogen per 1,000 square feet per year, spread across multiple applications.

Do not fertilize too early in spring. Wait until the grass has fully greened up and is actively growing, which usually means nighttime temperatures are consistently above 65 degrees Fahrenheit.

Stop fertilizing 6 weeks before your area's average first frost date. Late-season nitrogen produces tender growth that is easily damaged by cold.

Feeding Calendar

Spring

First application after full green-up, slow-release granular

Summer

Apply every 6–8 weeks with iron-containing formula

Early Fall

Final application at least 6 weeks before first frost

Late Fall & Winter

No feeding while dormant

What Is the Best Fertilizer for St. Augustine Grass?

St. Augustine Grass is a heavy nitrogen feeder. Look for a lawn fertilizer with a high first number, like 15-0-15 or 16-4-8, and make sure it contains iron. Iron keeps St. Augustine its deep green color without pushing excessive top growth.

Granular slow-release fertilizer is the best choice for lawns. It feeds evenly over 6 to 8 weeks and is easy to apply with a broadcast spreader. Avoid quick-release nitrogen, which can cause a growth surge followed by a crash.

St. Augustine also benefits from potassium for root strength and disease resistance. A 15-0-15 ratio (nitrogen and potassium, no phosphorus) is a popular choice in areas where soils already have plenty of phosphorus.

Synthetic

Scotts Turf Builder Southern Triple Action

Feeds, kills weeds, and prevents fire ants in one application. Designed specifically for Southern grasses including St. Augustine.

Lesco Professional 16-4-8 with Iron

Professional-grade slow-release granular used by lawn care companies. Apply at 6.25 lbs per 1,000 sq ft every 6 to 8 weeks.

Organic

Milorganite 6-4-0

Slow-release organic nitrogen from biosolids. Will not burn even if over-applied. Contains iron for deep green color.

Espoma Organic Lawn Food 9-0-0

All-natural feather meal formula that feeds for up to 3 months. Apply at the bag rate for warm-season grasses.

How Do I Fertilize My St. Augustine Grass?

Mow before you feed

Cut your lawn 2 to 3 days before fertilizing so the granules can reach the soil instead of sitting on top of tall leaf blades.

Calibrate your spreader

Set your broadcast spreader to the rate listed on the fertilizer bag for St. Augustine Grass. Too much in one pass causes burn streaks.

Apply in two passes

Walk the spreader in one direction across the lawn, then make a second pass perpendicular to the first. This ensures even coverage without missed strips.

Water in within 24 hours

Run your sprinklers for about 15 to 20 minutes after applying to wash the granules off the grass blades and into the soil. Granules left on wet leaves can burn.

Skip stressed areas

Do not fertilize sections of the lawn that are drought-stressed, diseased, or newly sodded. Feed these areas only after they recover and are actively growing.

Got More Questions?

Can I use coffee grounds on my St. Augustine lawn?

A light scattering of coffee grounds is fine as organic matter, but they contain very little nitrogen compared to what a lawn needs. They are not a substitute for proper lawn fertilizer.

What happens if I over-fertilize St. Augustine Grass?

You will see yellow or brown burn patches where the fertilizer was concentrated. Heavy nitrogen also makes St. Augustine more susceptible to chinch bugs and fungal diseases like brown patch and gray leaf spot.

Why is my St. Augustine Grass yellow even though I fertilize?

Yellowing despite fertilizing usually points to an iron deficiency, not a nitrogen problem. Apply a supplemental iron product (like ironite or chelated iron spray) between your regular fertilizer applications.

Should I fertilize St. Augustine Grass in winter?

No. St. Augustine goes dormant when temperatures drop below 55 degrees Fahrenheit. Fertilizing dormant grass wastes product and can pollute waterways through runoff.

Is it okay to fertilize right after mowing?

It is better to fertilize 2 to 3 days after mowing. Freshly cut leaf blades have open wounds that can absorb fertilizer salts and burn. Let the tips heal first.

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About This Article

Kiersten Rankel M.S.

Botanical Data Lead at Greg · Plant Scientist

About the Author

Kiersten Rankel holds an M.S. in Ecology & Evolutionary Biology from Tulane University. A certified Louisiana Master Naturalist, she has over a decade of experience in science communication, with research spanning corals, cypress trees, marsh grasses, and more. At Greg, she curates species data and verifies care recommendations against botanical research.

See Kiersten Rankel's full background on LinkedIn.

Editorial Process

Fertilizer recommendations verified against Stenotaphrum secundatum growth data from Greg's botanical database, cross-referenced with USDA hardiness zone data and published horticultural research.

433+ Greg users growing this plant

USDA hardiness zones 8a–11b

Citations:
NC State Extension
Royal Horticultural Society
UF IFAS Extension
USDA Plants Database

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