St. Augustinegrass Care Guide — Georgia

Nitrogen Budget — A Regional Number, Not a Georgia One

Aim for about 2.5 pounds of nitrogen per 1,000 square feet across the season, and treat 4 pounds as the ceiling — beyond that, warm-season lawns push soft, disease-prone growth rather than density. These figures come from NC State Extension's Carolina Lawns guidance for the Southeast, not a Georgia-specific publication for this grass, because Georgia's own species calendar for St. Augustine isn't available in a form we can quote here. Confirm the numbers against University of Georgia Extension and your county extension office before building a program around them.

Mowing Height by Season

St. Augustine does best kept in a 2.5 to 4 inch band, with about 3.25 inches as a solid target through spring, summer, and fall — tall enough to support root depth and the shade tolerance this grass is known for, without tipping into scalp territory. Like the nitrogen figures, this mowing band is regional Southeast guidance rather than a Georgia-specific number, so check it against your county extension office's recommendation for your part of the state.

Never remove more than a third of the blade in a single mow. If the lawn has gotten ahead of you, step the height down over two or three cuts instead of scalping it back in one pass.

The Season Timeline

A pre-emergent herbicide is timed to soil temperature, not the calendar — the window here runs Feb 19 to Mar 19, centered around Mar 5, as soil rises through 55°F ahead of summer annual weed germination.

Hold off on fertilizer until green-up is complete and soil is consistently above 65°F; feeding a half-dormant lawn mostly feeds weeds. The first feeding window runs Mar 27 to Apr 24, a second falls May 20 to Jul 1, and a third centers on Jul 15 to Aug 26. Treat that August window as the season's last real nitrogen feeding — more on why below — and aim for the earlier part of it rather than the end, so the grass has the rest of the warm weeks to harden off.

Because St. Augustine spreads and repairs only from sod or plugs, late spring into early summer — Apr 24 to Jun 19, as soil warms through 70°F — is the window for filling bare or thin spots while the grass is actively growing enough to knit in before fall.

As soil cools back through 70°F in late summer, a fall pre-emergent (Aug 28 to Oct 3) heads off winter annual weeds like annual bluegrass, henbit, and chickweed in the dormant or semi-dormant lawn. That same product blocks grass seed too, including any ryegrass overseed, so it's one or the other — not both, in the same spot.

Watering

Aim for about 0.75 inch of water a week, split into two deep soakings of about 0.5 inch each, early in the morning so the lawn dries before night — wet turf overnight invites disease. In sustained heat, that target climbs: roughly a quarter inch more when highs sit near the mid 80s, up to about half an inch more when three or more days push near 90, capped so the soil can absorb it without runoff.

Herbicide Sensitivity — Read the Label Every Time

This is the top safety point for St. Augustine: many common broadleaf lawn herbicides, and ordinary big-box weed-and-feed products that a bermuda or zoysia lawn shrugs off, will injure or kill this grass outright. Atrazine-based products are the common exception rather than the rule, and they come with their own temperature ceilings to observe. Never assume a product is fine for this grass — confirm St. Augustine is specifically named on the label before anything goes down, and treat the label as the law, not a suggestion.

Chinch Bugs — Not Just Grubs

Chinch bugs are the number-one killer of St. Augustine lawns, and they're routinely mistaken for drought stress: the damage shows up as a dry-looking patch, usually in the hottest, sunniest part of the yard, that doesn't green back up no matter how much water goes on it. A grub preventive does nothing against chinch bugs — they're a different insect entirely. If you've put down a grub product and consider insect risk handled, this grass is still exposed to the thing most likely to kill it. Scout hot, sunny areas through the season regardless of whether a grub preventive has gone down.

No Seed — Sod and Plugs Only

There is no viable commercial seed for St. Augustinegrass. It establishes and repairs only from sod or plugs, which is exactly why a large dead patch — from chinch bugs, herbicide injury, or winter cold — is an expensive problem rather than a minor one. Whatever the cause, the fix is sod or plugs, timed to the late spring through early summer window while the grass is actively growing.

Fall Potassium Is Not a Second Nitrogen Feeding

On this calendar, the last real nitrogen feeding and the fall potassium window sit close together — Jul 15 to Aug 26 for nitrogen, Sep 10 to Oct 22 for potassium — and they can even overlap. Many bagged winterizer products carry meaningful nitrogen alongside the potassium, and that combination amounts to a late-season feeding. Late-season nitrogen is what drives winter injury in a warm-season grass. Read the first number on the bag: for the fall application, pick a product that's genuinely low in nitrogen and high in potassium, and treat the August feeding as the last nitrogen of the year, full stop. Pulling that last nitrogen feeding toward the earlier part of its window gives the grass the rest of the warm weeks to harden off and rebuild the reserves it lives on through dormancy.

If You Plan to Overseed

St. Augustine itself is never seeded, but many Georgia lawns overseed with a cool-season grass for winter color, or reseed a repaired area with something other than St. Augustine. If that's the plan, the same herbicide timing rules apply everywhere else: if you've recently applied a broadleaf herbicide, wait about 6 weeks (42 days) before seeding. If you've recently put down a crabgrass pre-emergent, wait about 12 weeks (84 days) before seeding — a pre-emergent that stops crabgrass will stop grass seed just as effectively, cool-season or warm.

Gear this schedule assumes

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Rain gauge

Any $10 gauge works. You need it to hit the 0.75 in/week target above without guessing.

Soil thermometer

The seed and pre-emergent windows above are soil-temperature windows — a $15 probe beats calendar guessing.

Broadcast spreader

Needed for even fertilizer and seed rates. A basic rotary spreader covers most lawns.

Oscillating sprinkler + hose timer

Enough to water deeply and consistently if you have no in-ground system.

Smart irrigation controller

Only if you have an in-ground system — a Rachio-style controller automates the watering schedule.

None of this replaces a look from University of Georgia Extension or your county extension office, especially this far south where St. Augustine's shade and salt tolerance make it the right call in a way it wouldn't be further north. Keep the label in hand, watch for chinch bug damage in the hot, sunny stretches, and let the last nitrogen feeding come early enough that the grass heads into dormancy with something in reserve.

More guides

St. Augustinegrass in other states

Louisiana · North Carolina · Texas · Virginia

Other grasses in Georgia

Bermudagrass · Centipedegrass · Tall Fescue · Zoysiagrass