Crabgrass is one of the most stubborn and aggressive grassy weeds. Because it produces thousands of seeds per plant, a proactive approach is absolutely essential to prevent it from dominating your yard during the hot summer months.
The Crabgrass Lifecycle
Crabgrass is a summer annual. It germinates in the spring, grows vigorously through the summer heat, and dies with the first hard frost—but not before dropping seeds for the next year. Breaking this cycle is the key to eradication.
The Importance of Soil Temperature
Crabgrass seeds germinate when soil temperatures reach 55-60 degrees Fahrenheit. Monitoring local soil temperatures, or paying attention to natural indicators like blooming forsythia bushes, tells you exactly when to deploy your preventative treatments.
Applying Pre-Emergent Herbicides
The most effective weapon against crabgrass is a pre-emergent herbicide. Applied just before soil temperatures reach the germination threshold, it forms a barrier that kills the seedling as it attempts to sprout.
Post-Emergent Solutions
If crabgrass breaks through, post-emergent herbicides containing quinclorac can be effective, especially when the plant is young. Once crabgrass matures and spreads its tillers, it becomes highly resistant to chemical treatments.
Cultural Prevention
Crabgrass loves hot, dry conditions and thin turf. Mowing high (at least 3 inches) shades the soil, keeping it cool and preventing seed germination. Deep, infrequent watering encourages deep grass roots, giving your turf an edge over shallow-rooted crabgrass.