St. Augustinegrass Care Guide for Louisiana

Nitrogen Budget for the Season

Aim for about 2.5 lb of nitrogen per 1,000 square feet across the whole season, and treat 4 lb as the ceiling you shouldn't cross. That total gets spread out rather than dumped in one application: a spring green-up feeding once soil is consistently above 65°F and the lawn shows about 50% green-up (Mar 7 to Apr 4, centered Mar 21), a summer feeding during peak growth (May 10 to Jun 21), a second summer feeding to sustain density through late heat (Jul 15 to Aug 26), and a fall application that leans high-potassium and low-nitrogen (Oct 21 to Dec 2) to help the grass harden off before dormancy rather than push new growth into the cold.

Mowing Height by Season

St. Augustinegrass does best kept in the 2½ to 4 inch band, and for spring, summer, and fall the target sits at 3¼ inches — that's the sweet spot for density without scalping.

Whatever the season, never remove more than one-third of the blade in a single mow. If the lawn has gotten away from you, step the height down gradually over two or three cuts rather than scalping it back in one pass.

The Season Ahead

Apply a pre-emergent herbicide as soil rises through 55°F, in the Jan 30 to Feb 27 window (centered Feb 13), to head off summer annual weeds before the lawn fills back in.

St. Augustinegrass has no viable commercial seed, so bare or thin spots get filled with plugs or sod instead of seed — that window runs Apr 4 to May 30, centered May 2, once soil is rising through 70°F and the grass is actively growing enough to knit in before fall. Keep new plugs well watered until they're established.

If you're treating broadleaf weeds, the window runs Apr 16 to Jun 3. Confirm the label specifically lists St. Augustinegrass before applying — some broadleaf herbicides injure this grass — and avoid spraying above roughly 90°F or when the lawn is under drought stress. The label is the law here.

Most lawns never need a grub preventive. If you've had grub damage before, or grubs are a known problem locally, the window to apply and water one in — before eggs hatch into root-feeding larvae — runs Apr 26 to Jun 7. Otherwise, skip it and scout for damage instead.

As soil cools through 70°F in the Aug 28 to Oct 3 window, a fall pre-emergent stops winter annual weeds like annual bluegrass, henbit, and chickweed before they germinate. It also blocks grass seed, including any winter ryegrass overseed, so it's one or the other, not both.

Pull an annual soil test sometime in the Jul 27 to Oct 25 window, while the grass is still active, to guide lime and nutrient decisions. And if you aerate, late spring — Apr 9 to May 21 — works best, once soil is above 65°F and the lawn is well into active growth.

Watering

Aim for about ¾ inch of water a week, split into two deep soakings of about ½ inch each, applied early in the morning so the lawn dries out before night. Watering deep and infrequent encourages roots to grow down instead of staying shallow.

In sustained heat, that weekly target climbs — about a quarter inch more when highs sit near the mid-80s, up to about a half inch more when three or more days push near 90 — capped at that level so the soil can actually absorb it instead of running off.

Timing Conflicts to Keep in Mind

These are conditional rules to plan around, not events that have already happened on your lawn. If you've recently applied a broadleaf herbicide, wait about 6 weeks (42 days) before seeding anything. If you've recently put down a crabgrass pre-emergent, wait about 12 weeks (84 days) before seeding.

Since St. Augustinegrass itself is established from plugs or sod rather than seed, these gaps mainly matter if you're overseeding with ryegrass for winter color or seeding a separate area of the yard — worth checking before you plan either around a recent herbicide or pre-emergent application.

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 needs to be exact to the day — soil temperature and how the grass is actually responding matter more than hitting a date on a calendar. Keep an eye on both, follow the product label for anything you apply, and adjust the timing to what's actually happening in the yard.

More guides

St. Augustinegrass in other states

Georgia · North Carolina · Texas · Virginia

Other grasses in Louisiana

Centipedegrass