St. Augustine Grass Lawn Care Schedule — USDA Zone 10

Timing: mid-January to early February

Apply a pre-emergent herbicide as soil temperatures climb through the low 50s°F — before they reach the ~55°F at which crabgrass germinates — to stop summer weeds before they start. Whether a second pass is called for, how long after the first, and what the season's total may add up to are all set by the active ingredient and rate on your label, not by a general rule: some products are labeled for a split program and some are a single application for the year. Pick the product first, then read its split-application and maximum-annual-rate directions. Zone 10 gives this one very little room: only about 11 days separate the median last freeze (January 25) from the close of this window. Miss it and there is no second chance at a pre-emergent this spring — plan on treating the whole lawn in a single pass rather than splitting it over two weekends. One thing this zone makes easier: st. augustine grass is established from sod, plugs or sprigs rather than seed, so the usual pre-emergent-versus-seeding conflict does not apply to the lawn itself.

⚠️Most pre-emergents block desirable grass seed as well as weed seed, so a residual pre-emergent and seeding the same ground are mutually exclusive — pick one — though a few products (e.g. siduron, or mesotrione on labeled species) are made for use at seeding.

Timing: mid-January to mid-February

Warm-season turf begins breaking dormancy as soil temperatures reach about 55°F, but it isn't actively growing until the soil warms to roughly 65°F. Do not scalp St. Augustine grass to bring it out of dormancy. The low spring reset is a bermuda and zoysia practice; on St. Augustine grass it thins the stand rather than resetting it. Its own recommended height of 2–4″ is where its reserves and its shade and weed tolerance live, whether that number is high or low. Rake or lightly dethatch to lift the matted dormant leaf, mow at the normal height, and follow the one-third rule: never remove more than a third of the blade in one pass. Don't fertilize until it's about 50% green and actively growing — roughly when soil temperatures hold above ~65°F. Zone 10's median last spring freeze is around January 25, which is 10 days AFTER this window opens. So the early part of it is cleanup on grass that can still be frosted, and st. augustine grass is a high-cut grass (2–4″), so there is no scalping headroom to work with — rake the debris out rather than cutting it out. Nothing you apply before that freeze date is working on a lawn that is actually growing.

Timing: mid-February to early April

Make the first fertilizer application 2–4 weeks after full green-up, once the lawn is actively growing. Feed about 2–4 lbs of nitrogen per 1,000 sq ft per year across the warm months. An iron supplement deepens color without forcing the excess top growth that heavy nitrogen would.

⚠️Several weed killers that are fine on other lawns will damage St. Augustine — confirm the label lists it by name before spraying. Keep nitrogen at or below ~1 lb per 1,000 sq ft per feeding.

Timing: early March to mid-June

Core-aerate (and dethatch if the thatch layer is over about ½") during the peak growing season, when warm-season turf recovers fastest. Avoid aerating dormant or drought-stressed turf. Zone 10 has room here — about 196 days of growing season stand between the close of this window and the median first freeze on December 28, and st. augustine grass spreads, so it closes the holes itself given growing weather. With that much recovery the constraint is soil moisture rather than the calendar.

Timing: late April to mid-September

Summer is the warm-season growth peak. Feed about 2–4 lbs of nitrogen per 1,000 sq ft per year across the warm months. An iron supplement deepens color without forcing the excess top growth that heavy nitrogen would. Spread the annual budget across the season rather than applying it all at once.

⚠️Keep any single feeding at or below ~1 lb of nitrogen per 1,000 sq ft, and stop nitrogen about 6 weeks before your first expected frost.

Timing: late April to mid-September

Spot-treat broadleaf weeds during active growth, never on drought-stressed turf. Watch for insect and disease pressure in hot, humid weather and treat problem areas rather than the whole lawn.

Timing: late September to early November

Give a final feeding in early fall, then stop nitrogen — late-season nitrogen pushes tender growth into frost. How late this can safely run is regional: closer to the Gulf the grass is still growing well into autumn, while at the cold edge of its range this window closes weeks earlier, which is why it is pinned to your own freeze normals rather than to a month. Zone 10 is mild enough that the six-week rule barely bites: nitrogen has to stop by about November 16 ahead of the median first freeze on December 28, and the window above still runs to November 5. This card is the LAST of st. augustine grass's 2–4 passes, not the program — its 2–4 lb range spreads the rest across the season — and zone 10's mildness is what leaves room to place it without crowding the freeze.

⚠️Stop nitrogen about 6 weeks before your first expected frost.

Timing: late September to late December

Fall is the best time to take a soil test: lime or sulfur has the winter to react, and you go into spring with a real pH and fertility picture instead of guesswork. Send it to your state extension lab and tell them which grass you grow — the target pH is species-specific, and a lab that knows you have centipede reports against a different range than one assuming bluegrass.

Timing: early October to early November

A fall pre-emergent applied before soil cools below about 70°F controls winter annual weeds like Poa annua and henbit. Do not wait for cold weather to cue this in zone 10 — the first freeze is not until about December 28, a good 84 days after the window opens. Winter annuals germinate on soil falling through about 70°F, which happens here while the air is still summer-warm, so the lawn will not feel autumnal when the application is already due.

Timing: late December

Wherever winter brings frost, expect a brown, dormant lawn from the first frost until spring green-up: hold off on fertilizer and pre-emergent, and give a light watering during extended winter drought to prevent desiccation. In the warmest, nearly frost-free areas (roughly USDA zone 10 — south Florida, coastal Southern California), the lawn often just slows down and stays partly green rather than going fully dormant; keep mowing and watering lightly as needed, and it can still use a little nitrogen or iron for winter color. Zone 10 barely has a dormant season to speak of — about 28 days between the first fall freeze and the last spring one. Expect a slowdown and some color loss rather than a full brown-out, and keep mowing at a reduced frequency toward the top of st. augustine grass's 2–4″ range. st. augustine grass carries a mild winter like this one without much help.