Texas Turf Pros • Updated July 2026 • 6 min read

When to Apply Pre-Emergent in Central Texas (Go by Soil Temperature, Not the Calendar)

Ask ten neighbors when to put down pre-emergent and you’ll get ten dates. The truth is there is no date — there’s a soil temperature. Get that right and you prevent crabgrass, grassburs, and winter weeds before they ever exist. Miss it by two weeks and you fight them all year.

Why pre-emergent is the backbone of a weed-free lawn

Pre-emergent herbicides don’t kill weeds you can see. They form an invisible barrier in the top layer of soil that stops weed seeds as they germinate. That matters because the worst lawn weeds in the Highland Lakes — crabgrass, grassburs (sandburs), and poa annua — are annuals. Every plant you see this year came from a seed this year. Block the seeds and there is nothing to fight later.

On a golf course, pre-emergent timing is treated like a payroll deadline — because one missed window means a season of visible weeds on turf that thousands of people look at. Home lawns work exactly the same way; the stakes are just quieter.

The spring window: soil at 55°F, usually mid-February to early March

Crabgrass begins germinating when soil temperature at a couple inches deep holds around 55°F for several consecutive days. In Kingsland, Marble Falls, and the rest of the Highland Lakes, that typically happens in late February — noticeably earlier than the Texas average, because our granite-derived soils warm quickly.

• Too early is safer than too late. Applied a few weeks early, the barrier just sits and waits. Applied after germination, it does almost nothing.
• Grassburs germinate slightly warmer (around 52–55°F) and keep germinating all summer — sandy lawns in Kingsland and Llano often need a split application, a second pass roughly 90 days after the first, to keep the barrier alive through summer.
• Water it in. Most pre-emergents must be watered into the soil within days of application to activate. A rain or one irrigation cycle does it.

The fall window: September to early October

The most skipped — and most valuable — application of the year. Winter weeds like poa annua (annual bluegrass), henbit, and chickweed germinate as soils cool in fall, grow quietly all winter, then explode in February. That pale, clumpy grass that seeds all over Highland Lakes lawns in late winter? It was preventable back in September.

A fall barrier applied when soil temperatures drop toward 70°F stops the whole cycle. If your lawn looks great all summer and terrible every February, this is the application you’ve been missing.

The three mistakes we see most

1. Applying by the calendar

A warm winter can open the spring window two or three weeks early. We schedule by measured soil temperature, which is why timing rarely slips.

2. One application, no follow-through

Pre-emergent barriers break down in heat and sun — typically lasting 3–4 months. One February application does not cover a nine-month Texas growing season.

3. Pre-emergent on a lawn you plan to seed

The barrier can’t tell a weed seed from a grass seed. If you’re planning to overseed or plant new turf, the program has to be planned around it.

What a full-season program looks like here

For most Highland Lakes lawns, we run a spring barrier (split for sandy, grassbur-prone soils), post-emergent cleanup of anything that slips through, fertilization matched to your grass type and soil test, and the fall barrier that keeps next February clean. Every visit ends with a service note telling you what went down and why.

Quick answers

Is it too late to apply pre-emergent if weeds are already up?

For those weeds, yes — pre-emergent only stops seeds as they germinate. But it's never pointless: a late barrier still blocks the next flush of seeds, and the weeds that are already up can be handled with a selective post-emergent treatment.

Do I need pre-emergent twice a year?

In Central Texas, yes — a spring application (late February) for crabgrass and grassburs, and a fall application (September–October) for poa annua, henbit, and other winter weeds. Sandy, grassbur-prone lawns often benefit from a split spring application as well.

Will pre-emergent hurt my Bermuda or St. Augustine?

Applied at label rates on an established lawn, no — the products we use are selective and turf-safe. The exception is lawns being seeded or sodded, where timing has to be planned around the barrier.