Turf - Encouraging Turf in areas With Crabgrass and Other Summer Weeds

With frost just around the corner, summer annual grass weeds such as crabgrass will soon be killed and summer perennial grass weeds such as wiregrass and nimblewill will be going dormant. Now is the time to try to thicken up stands of cool season turf species. The following is a short article on the subject.

With the cooler nights of fall quickly descending upon us warm-season, annual, grassy weeds such as crabgrass are coming to the end of their life cycle. In much of the state, crabgrass is beginning to show the first signs of the approaching fall season by producing seed heads and turning purple. The first few frost will quickly finish this year’s crabgrass crop. Therefore, it is very important to remember the fall fertilizer applications. A sound fall fertility program will encourage the desirable turfgrasses in the lawn to fill in areas formerly occupied by the summer’s bumper crop of crabgrass. This will pay dividends next year when the new crop of crabgrass has less “open space” in the lawn to germinate and take advantage of. If you didn’t get your fertilizer down in September, there’s still time for an October and a November application.

Crabgrass turns purple with the onset of cooler fall nights.

Adapted from "Purple Crabgrass?" by Glenn Hardebeck, Turfgrass Research Agronomist, Agronomy Department, Purdue University, from an article accompanying the Purdue Plant and Pest Diagnostic Lab Picture of the Week for October 2, 2006.