Crabgrass is a relentless annual grassy weed that thrives in Texas’s prolonged, hot growing seasons. Although the plant dies off with the first frost, it leaves behind a massive number of seeds ready to sprout the following spring, ensuring a recurring infestation. Successfully eliminating and preventing crabgrass requires a strategic, multi-faceted approach. Focusing on precise timing, chemical application, and long-term turf health is the most effective way to maintain a clean, vibrant lawn.
Timing is Everything: When Crabgrass Germinates in Texas
Controlling crabgrass depends on understanding its germination trigger: soil temperature. Seeds begin to sprout when the soil temperature at a two-inch depth consistently reaches 55 degrees Fahrenheit for three to five consecutive days. Applying a pre-emergent herbicide before this threshold is reached is necessary for the product to establish its protective barrier in the soil.
This soil temperature-based timing means the application window varies significantly across Texas. Homeowners in South Texas must apply preventative treatments weeks before those in North Texas, where warmer weather arrives later. For instance, Central Texas often hits this mark in late February to early March, while the Dallas-Fort Worth area typically sees it in early to mid-March. Relying on a soil thermometer or local extension data is more reliable than using air temperature or a fixed date.
Stopping Crabgrass Seeds: Pre-Emergent Control Methods
Pre-emergent herbicides create a chemical barrier in the top layer of the soil that prevents crabgrass seeds from completing germination. These products must be applied before the seeds sprout, as they have no effect on already visible, established plants. The active ingredients most effective and commonly used in Texas lawns are prodiamine and pendimethalin.
Application requires careful attention for maximum efficacy. The herbicide, whether granular or liquid, must be watered into the soil immediately after application to activate the protective barrier. Since Texas has an extended growing season, a single spring application is often insufficient for season-long control. A second application, typically 8 to 10 weeks after the first, is recommended to maintain the barrier through the long, hot summer months.
Eliminating Established Weeds: Post-Emergent Control Methods
When crabgrass has already emerged, a post-emergent herbicide is required to kill the plant. The most effective chemical for controlling established crabgrass in warm-season Texas turf, such as Bermuda grass, is quinclorac. This selective systemic herbicide is absorbed through the foliage and translocated throughout the weed, causing abnormal growth and eventual death.
Homeowners must exercise caution, as quinclorac is generally not safe for use on St. Augustine grass. For smaller outbreaks, hand-pulling is a viable, non-chemical option, but it is important to remove the entire root structure. Treating young crabgrass plants, ideally before they develop more than three to five leaves, is much easier and more effective than controlling mature plants that have already started producing seeds.
Cultural Practices for Long-Term Control
The strongest defense against recurring crabgrass is maintaining a dense, healthy turf that outcompetes the weed for light and space. Crabgrass requires a significant amount of light to germinate, making a taller lawn an effective natural barrier. Mowing your turf at the highest recommended height for your specific grass type, such as three to four inches for St. Augustine, shades the soil and keeps it cooler, inhibiting seed germination.
Proper watering techniques also discourage crabgrass while promoting a strong lawn. Deep, infrequent watering encourages the turfgrass to develop deep, robust root systems. Conversely, shallow, frequent watering keeps the soil surface moist, which is exactly what crabgrass needs to thrive. Additionally, following a proper fertilization schedule helps maintain the turf’s density, creating a healthier environment where opportunistic weeds like crabgrass cannot easily establish a foothold.