The Best Times to Apply a Crabgrass Preventer in Central Texas

Crabgrass Seeds

• Crabgrass is an annual grass that emerges in the spring, germinates all through the summer and dies off with the first frost of fall. It propagates through seeds, and unfortunately is a prolific seed producer. Just because you didn't have a problem with crabgrass last year doesn't mean you won't have to deal with it this year. Crabgrass seeds can bank in the soil and thatch, where they bide their time waiting to take advantage of an injured or weak spot in your lawn.

Pre-Emergent

• When crabgrass first appears, it's hard to identify, because all that is visible is the skeleton. Once it's mature enough to identify, laying down a crabgrass preventer won't do much good. Your best bet is to apply pre-emergent herbicide around two weeks before you expect crabgrass to appear, according to the Texas A&M AgriLife Extension. The tricky part is determining when that time frame will occur, since crabgrass germinates from April through September, depending on where you live.

Soil Temperature

• Experience might the best teacher when it comes to estimating when crabgrass might emerge, but science provides a few tools that can at least reduce some of the guess work. Crabgrass seeds can germinate once the soil temperature reaches from 55 to 60 degrees for several days. Taking soil temperature readings with a soil thermometer will give you a good indication of when germination might take place. If you don't have a soil thermometer, keep a sharp eye on the shrubs and trees. When they start to bud, chances are crabgrass seeds are getting ready to germinate.

Preventer or Seed

• Crabgrass needs sunlight to germinate. A thick, healthy lawn that shields crabgrass seeds from the sunlight is your best defense against a crabgrass invasion. While weeds, including crabgrass, are less problematic in lawns with a thick turf, chances are you have some weak areas or bare spots where crabgrass can get a foothold. Your choices range from putting down a pre-emergent to putting down fresh sod or grass seed. Most crabgrass preventers that are available to homeowners aren't selective in their effectiveness. They'll likely prevent desirable grass seed from germinating as well.