The Gulf Coast, Florida, south Texas and the desert Southwest. The longest growing season of the three, and the only one where many warm-season lawns barely go dormant at all.
- Growth
- slowing~72°F soil, cooling
- Mow
- 1.5–2"every 10-14 days
- Water
- Water on demand now, not on a schedule — the lawn's use drops with the soil temperature. Irrigate when the leaf blades fold in half lengthwise, the colour goes blue-grey, or footprints stay visible after you walk across it. Put down 1/2 to 3/4 in when you do, about once a week or less; UF/IFAS puts the cooler months at one watering day a week. Before sunrise, so the blades dry as the sun comes up.
Do thisEvery week this month
A warm-season lawn grown at a consistent height and cut often enough to never lose a third of its blade is the cheapest weed control there is — a dense canopy leaves weed seed nowhere to germinate.
When: throughout the month
Steps
- Cut on a schedule, not when the lawn looks long.
- Never remove more than a third of the blade in one pass.
- Change direction each time so the grass does not learn a lean.
- Re-sharpen the blade every 20-25 hours of cutting.
Do this
Poa annua, henbit and chickweed germinate in autumn as the soil falls back through the high 60s. Catching them now is the difference between a clean lawn in February and spending February spraying — and by February the only option left is post-emergent on a dormant lawn.
When: as the 7-day mean soil temp falls through 67-70 F at 4 in (week 1 of the month)
Rate: per label for your grass and your square footage; if you are planning a second application, the label's ANNUAL maximum is the number that governs
Product: pre-emergent herbicide, active ingredient prodiamine or dithiopyr, per label
Label: CHECK THE LABEL LISTS YOUR GRASS. Not every pre-emergent is labeled for St. Augustine or centipede, and the ones that are often carry a lower rate for them than for bermuda — on those two grasses, a product whose label does not name your grass is a product that can thin it. Purdue AY-10 also lists pendimethalin, oxadiazon and benefin; residual runs 60-120 days depending on rate.
Soil temperature: 67–70°F soil at 4-inch depth.
Air temperature: Do not apply above 90°F air temperature — above that you risk injuring the lawn.
Steps
- Go by falling soil temperature: apply as the 7-day mean drops through 67-70 F at 4 in.
- Water in with half an inch within 24 hours.
- Do not aerate after applying.
- One application usually holds the winter. A second at half rate 8-10 weeks later extends it ONLY IF THE LABEL ALLOWS a sequential application and you stay inside its annual maximum — check before you buy, not after you have applied the first one.
NC State Extension, Carolina Lawns — pre-emergent timing · Texas A&M AgriLife Extension, L-5340 — Lawn Care
Full weed-control guide →Worth doing
St. Augustine and centipede are injured by the 2,4-D products that are safe on bermuda, and the damage often shows up a week later as yellowing that looks like disease. Celsius WG is the first choice because it is labeled for both and holds up in heat better than the alternatives.
When: on an actively growing lawn, on a sunny day above 55 F and below the 85 F ceiling
Product: selective post-emergent herbicide labeled for this grass, active ingredient thiencarbazone + iodosulfuron + dicamba (Celsius WG)
Label: Atrazine is NOT a safe substitute: Texas A&M EHT-144 says Floratam is not tolerant of it, and Floratam is the most common St. Augustine cultivar.
Air temperature: Spray on a day above 55°F; not above 85°F. Below the floor the weed is not actively growing and the application is wasted; above the ceiling you injure the lawn.
Steps
- Use Celsius WG as the first option. It is labeled for St. Augustine and centipede.
- If you use a southern 2,4-D formulation instead, treat 85 F as the ceiling, not 90 F, and expect more injury risk.
- Never use a standard 2,4-D lawn weed killer on these two grasses.
- Spray on a sunny day with the high above 55 F. Below that the weeds are not actively growing and the application is wasted.
- Mow 2-3 days before spraying. Do not spray stressed turf or newly laid sod.
Clemson Cooperative Extension, Centipedegrass Yearly Maintenance Program (HGIC 1215) · Texas A&M AgriLife Extension, L-5340 — Lawn Care
Full weed-control guide →Worth doing
Large patch infects in autumn as soil temperatures fall, but the circular dead patches do not appear until spring — so the only useful treatment is a preventive one applied now. Treating in spring, when you can see it, is treating damage that is already done. NC State: "For centipedegrass and St. Augustinegrass, applications should be initiated when soil temperatures decline to 80 F for 5 or more consecutive days." Centipede is the most susceptible turfgrass there is to this disease.
When: once the 4-inch soil temperature has declined to 80 F for 5 or more consecutive days
Product: preventive turf fungicide, active ingredient azoxystrobin or propiconazole
Soil temperature: Below 80°F soil at 4-inch depth.
Steps
- Apply once the 4-inch soil temperature has declined to 80 F for 5 or more consecutive days — not when it first touches 80 F.
- Only worth doing if you have had large patch before, or the lawn is shaded and stays wet.
- Water in lightly per the label.
- Stop nitrogen — NC State: "Do not apply nitrogen to warm-season grasses in the fall and spring." Feeding a lawn with active large patch makes it spread.
- Fix the drainage if water stands here. A fungicide on saturated ground is an annual expense, not a cure.