St. Augustinegrass Care Guide for Texas (Zone 8b)

Nitrogen Budget

For St. Augustinegrass, aim for about 2.5 lbs of nitrogen per 1,000 sq ft across the season, and treat 4 lbs as the ceiling. Spreading that total across the spring green-up, summer, and August feedings keeps growth steady without pushing the lawn toward the kind of soft, disease-prone growth that comes with too much nitrogen too fast. The fall potassium application later in the year is a high-K, low-N treatment, not part of this nitrogen total — it's there for cold hardiness, not growth.

Mowing Height by Season

St. Augustinegrass does best kept in the 2½ to 4 inch range, and 3¼ inches is the sweet spot for spring, summer, and fall alike — dense enough to shade out weeds without inviting scalp damage. If the lawn has gotten away from you and grown tall, don't drop it back to 3¼ inches in one pass. Never remove more than a third of the blade in a single mow; step the height down over two or three cuts instead.

The Seasonal Schedule

The spring pre-emergent herbicide window runs Feb 12 to Mar 12, centered around Feb 26, and is keyed to soil temperature crossing 55°F on the way up — this is what heads off summer annual weeds before the lawn fills in. Spring green-up fertilizer follows once soil is consistently above 65°F and the lawn shows about half green-up, in the Mar 20 to Apr 17 window.

Since St. Augustinegrass has no viable commercial seed, bare or thin spots get filled with plugs or sod rather than seed — that window runs Apr 17 to Jun 12, centered on May 15, once soil has warmed past 70°F and the grass is actively growing enough to knit in before fall. Keep new plugs well watered until they're established.

Summer carries two fertilizer windows — May 17 to Jun 28, and again Jul 15 to Aug 26 — to sustain density through peak heat, with the August round being the last heavy nitrogen application before the fall transition. Spring core aeration (Apr 16 to May 28) and a summer wetting agent (May 8 to Jul 7) both support the lawn through that same stretch of heat and growth. An early-summer grub preventive window (May 3 to Jun 14) exists for lawns with a known grub history — most lawns don't need it; scout for damage instead of treating automatically.

As the season turns, a fall pre-emergent for winter weeds goes down as soil cools through about 70°F, in the Aug 28 to Oct 3 window — this targets annual bluegrass, henbit, and chickweed before they germinate. Fall potassium follows in the Sep 14 to Oct 26 window to build cold hardiness heading into dormancy, and an annual soil test (Jul 27 to Oct 25) is worth collecting while the grass is still active, to guide any lime or nutrient adjustments for next year.

Watering

Aim for about ¾ inch of water a week, split into two deep soakings of about ½ inch each, done early in the morning so the lawn dries before nightfall — wet grass overnight invites disease. In sustained heat, that weekly target rises: about a quarter inch more once highs sit near the mid 80s, and up to a half inch more when three or more days push near 90, capped so the soil can actually absorb it rather than running off.

Timing Conflicts to Watch

A few product categories interact with timing in ways worth knowing before you reach for one. 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 — that pre-emergent doesn't distinguish between weed seed and grass seed.

This matters most if you plan to overseed with a cool-season grass like ryegrass for winter color, since St. Augustinegrass itself is established with plugs or sod, not seed. The fall pre-emergent window and a ryegrass overseed also conflict directly with each other — the pre-emergent blocks grass seed along with winter weeds, so it's one or the other, not both. And with any broadleaf herbicide, confirm the label lists St. Augustinegrass before applying — some broadleaf products injure it — and avoid spraying above roughly 90°F or when the lawn is under drought stress. The label is the law.

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 happen all at once — the value is in matching each step to what the soil and the calendar are actually doing, not to a fixed date. Keep an eye on soil temperature through late winter and late summer, and the rest of the schedule tends to fall into place.

More guides

St. Augustinegrass in other states

Georgia · Louisiana · North Carolina · Virginia

Other grasses in Texas

Bermudagrass · Centipedegrass · Tall Fescue · Zoysiagrass