Blog Post | LocalLandscape

When the first real cold front rolls through Fulshear, the St. Augustine in your yard starts to slow down. The weeds do the opposite. Fall is when most winter weeds sprout across Fort Bend County, though most people only notice them in late winter and spring. If you want a cleaner lawn next March, the time to act is now.

Here is a practical guide to fall weed control for Fulshear, Katy, Richmond and Simonton homeowners, based on Texas A&M AgriLife Extension guidance.

The winter weeds you will see in Fort Bend County lawns

Most winter weeds are winter annuals: they sprout from seed in fall, grow through the cool months, set seed in spring and die back as it heats up. Texas A&M AgriLife turfgrass specialists list these as the usual cool-season problems in Texas lawns:

Annual bluegrass (Poa annua) – a cool-season annual grass that AgriLife calls one of the more challenging lawn weeds.
Rescuegrass – another cool-season annual grass.
Henbit – square stems, scalloped leaves and small pinkish-purple flowers in whorls.
Common chickweed – low, mat-forming, with small white flowers. It thrives in cool, wet weather and fades when late spring turns hot and dry.
Carolina geranium – a broadleaf winter weed.
Lawn burweed (sticker weed) – low, ferny leaves that look harmless in winter, then form sharp, spiny burs in spring that catch on bare feet, shoes and pets.

Not sure what you have? AggieTurf has a free weed identification library with photos.

Why fall is the time to prevent winter weeds

Winter weeds germinate as soils cool. Once they are up and growing, you are chasing them. A pre-emergent herbicide (sometimes called a "weed preventer") works differently: it stops seedlings as they germinate, so it has to be in place before the seeds sprout. AgriLife describes pre-emergents as the most effective chemical option for tough annual weeds like annual bluegrass.

There is good news for St. Augustine owners. AgriLife notes that winter annual weeds are not common in St. Augustine, because a healthy, dense St. Augustine lawn competes well with most weeds. A fall pre-emergent is most useful where the turf is thin, where you have fought burweed or Poa before, or where bare soil is exposed.

When to apply a fall pre-emergent in the Houston area

AgriLife recommends timing by soil temperature, not the calendar. Its guidance: apply the fall pre-emergent when the top inch of soil cools to about 70°F for four to five consecutive days. AgriLife's charts place that window from late summer through October across Texas and note that timing can shift by several weeks depending on region and the year's weather. Their general advice is to expect it in September or October.

You can check it yourself with a soil thermometer (AgriLife says even a meat thermometer works) pushed about an inch into the soil. Some extension services use an air-temperature rule instead: Clemson Extension times fall pre-emergents for when nighttime lows reach 55 to 60°F for four nights in a row. In Fort Bend County, that first stretch of cooler nights after a fall front is a good reminder to start checking the soil. For local dates, call the Fort Bend County AgriLife Extension office.

Pre-emergent cautions

Choose a product whose label lists St. Augustine and the weeds you are targeting. AgriLife lists active ingredients such as dithiopyr, prodiamine, pendimethalin, isoxaben and indaziflam among those found in lawn products, but not every product is right for every grass.
Pre-emergents can injure newly laid or overseeded lawns. Don't use one if you plan to sod or overseed soon.
Read the bag before stacking products. Many "weed and feed" products already contain a pre-emergent, so adding a second one can over-apply.
Some pre-emergents can stain concrete. Sweep granules off driveways and sidewalks.

Post-emergent options and St. Augustine cautions

If weeds are already up, a selective post-emergent herbicide can help. AgriLife says post-emergent control works best while weeds are still small. Its St. Augustine calendar suggests treating winter annual weeds in late fall and early winter, as needed. Keep these St. Augustine rules in mind:

St. Augustine is sensitive to some herbicides. AgriLife specifically warns that 2,4-D can injure it. Check that the label lists St. Augustine before you buy.
Cultivar matters. AgriLife notes that Floratam St. Augustine is injured by atrazine.
Heat matters. AgriLife warns herbicides may damage the lawn when temperatures are above 90°F. Fulshear can still see warm days in early fall, so check the label's temperature limits before spraying.
Treat only healthy turf. AgriLife advises applying herbicides only when weeds are present and the grass is healthy. Clemson Extension also cautions that St. Augustine can be injured by broadleaf herbicides during spring green-up.

Non-chemical weed control that really works

AgriLife puts it plainly: the best form of weed control is a healthy, dense lawn. These habits make a big difference:

Mow at the right height. AgriLife generally recommends 2 to 4 inches for St. Augustine and suggests setting the mower at its highest setting or one notch below. Taller grass shades out weeds.
Don't scalp. Follow the one-third rule: never remove more than a third of the leaf blade at one time. AgriLife notes that frequent scalping exposes soil to sunlight, which helps weeds sprout and grow.
Keep mowing weeds through winter. AgriLife's St. Augustine calendar recommends mowing in winter, if needed, to keep winter annual weeds from flowering and setting seed.
Hand-pull small patches. Pull henbit, chickweed and young burweed while they are small, before they flower or form burs.
Water deeply and less often. Constantly wet soil favors cool-season weeds like chickweed and diseases like large patch.

Safety first: read the label

The label tells you which grasses a product is safe on, how much to use, when to apply and what protective gear to wear. Keep children and pets off treated areas for as long as the label directs, store products in their original containers out of reach, and follow the label on rain and watering-in. When in doubt, ask your county AgriLife Extension agent.

Thick turf is your best defense

Fulshear Lawn Mowing Service is a veteran-owned business run by James Henderson. We don't apply herbicides or fertilizer, because we focus on mowing and edging. Regular cuts at the right height help St. Augustine stay thick enough to crowd out winter weeds. Weekly or every-other-week mowing starts at $45 a visit, with edging available from $15. One-time cuts are available too. We serve Fulshear, Katy, Richmond, Simonton and Brookshire. Call (832) 338-2926 or view our profile to get on the schedule.

Fall Weed Control in Fulshear: Stop Winter Weeds