St. Augustinegrass Care Guide for North Carolina

Nitrogen: The Season Budget

Aim for about 2.5 pounds of nitrogen per 1,000 square feet across the season, and treat 4 pounds as the ceiling you don't want to cross. That budget gets split across the summer feeding windows — one centered in June, one in August — rather than applied all at once. Match the rate on the bag to this grass specifically; St. Augustine does not need, and does not benefit from, the heavier rates some other warm-season lawns can carry.

Mowing Height Through the Season

Keep St. Augustine in the 2½" to 4" band through spring, summer, and fall, with 3¼" as a good target for density without scalping. Whatever the height, never remove more than a third of the blade in one cut — if the lawn has gotten away from you, step the height down over two or three mowings instead of scalping it back in one pass.

Watering: Deep and Infrequent

Aim for about ¾ inch of water a week, split into two soakings of about ½ inch each, watered early in the morning so the grass dries out before night. In sustained heat, that target climbs — by about a quarter inch when highs sit near the mid 80s, up to about a half inch when three or more days push near 90 — but keep it capped so the soil can absorb it without runoff. Watering deep and infrequent trains roots to grow down instead of staying shallow.

The Seasonal Calendar

The spring pre-emergent window runs March 6 to April 3, centered on March 20, timed to soil warming through 55°F — it heads off summer annual weeds before the lawn fills in. Hold off on any fertilizer until green-up is actually complete; a warm week in March is not spring, and feeding a half-dormant lawn mostly feeds weeds and invites injury.

Since St. Augustine has no viable seed, establishment and repair happen with plugs or sod, in the window from May 9 to July 4, centered on June 6, once soil has warmed through 70°F. That's also the window to fill in bare or thin spots — keep new plugs well watered until they've knit in.

Summer fertilizer windows run May 28 to July 9 and again July 15 to August 26. Broadleaf weed control, if needed, falls May 4 to June 21, once the lawn is fully green and growing. A fall pre-emergent for winter annual weeds goes down as soil cools through 70°F, in the window from August 28 to October 3 — but it will also block any grass seed you put down, including a winter ryegrass overseed, so plan one or the other. Fall potassium runs August 24 to October 5. After the first killing frost, the lawn goes fully dormant into winter; brown is normal, and this is not the time to force green with fertilizer or water on a schedule.

Herbicide Sensitivity Is the Top Safety Point Here

This is the single most important thing to get right on a St. Augustine lawn: many common broadleaf herbicides, and ordinary big-box weed-and-feed products, injure or kill St. Augustine outright — the same products a bermuda or zoysia lawn shrugs off. Atrazine-based products are the common exception rather than the rule, and even those carry their own temperature limits for safe application. 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. As a general rule, broadleaf treatments should be avoided above about 90°F or when the lawn is under drought stress.

Chinch Bugs, Not Just Drought Stress

Chinch bugs are the leading cause of death in St. Augustine lawns, and they are routinely mistaken for drought. The signature is a patch — usually in the hottest, sunniest part of the yard — that looks dry and stressed but does not green back up no matter how much you water it. A grub preventive does nothing for this problem; grub products target a completely different insect. Treating grubs and considering insect risk handled leaves the lawn unprotected against the thing most likely to kill it. If a patch behaves like this, chinch bugs belong on the list of causes to check before anything else.

Cultivar Matters: Raleigh, Not Floratam

Not all St. Augustine is the same grass for cold-hardiness purposes. Raleigh is the benchmark cultivar for the Carolinas and the one to ask for by name this far north. Floratam, despite being widely stocked, is a Florida cultivar with essentially no cold hardiness — it is the wrong choice anywhere north of Florida, North Carolina's coastal corner included.

Fall Potassium Is Not a Second Nitrogen Feeding

The last summer nitrogen window and the fall potassium window sit close together on the calendar and can even overlap, and plenty of bagged winterizer products carry meaningful nitrogen alongside the potassium. Treated carelessly, that combination becomes a late-season nitrogen feeding — and late-season nitrogen is exactly what drives winter injury in a warm-season lawn. Read the first number on the bag. For the fall potassium application, choose a genuinely low-nitrogen, high-potassium product, not a general-purpose winterizer. And treat the last summer feeding, in its own window, as the season's last nitrogen, full stop — aim it toward the earlier part of that window rather than the end, so the grass has the rest of the warm weeks to harden off and build the reserves it depends on through dormancy.

If You Seed Anywhere in the Yard

St. Augustine itself only comes from sod or plugs, but if you overseed with ryegrass for winter color, or seed any other area of the lawn, the usual pre-emergent and herbicide timing rules still apply. If you've recently applied a broadleaf herbicide, wait about six weeks (42 days) before seeding. If you've recently put down a crabgrass pre-emergent, wait about twelve weeks (84 days) before seeding — the same chemistry that stops crabgrass will stop grass seed just as effectively.

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.

St. Augustine rewards a coastal North Carolina lawn with density and shade tolerance most other warm-season grasses can't match, but it asks for more care around herbicide labels, insect scouting, and late-season nitrogen than a bermuda or zoysia lawn would. Get the cultivar and the timing right, and the rest of the maintenance is straightforward.

More guides

St. Augustinegrass in other states

Georgia · Louisiana · Texas · Virginia

Other grasses in North Carolina

Bermudagrass · Centipedegrass · Fine Fescue · Kentucky Bluegrass · Tall Fescue · Zoysiagrass