Purple Crabgrass?

Glenn Hardebeck, Turfgrass Research Agronomist, Agronomy Department, Purdue University

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.  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.  For more on lawn fertility programs check out http://www.agry.purdue.edu/turf/pubs/ay10.htm

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Crabgrass does well next to heat sinks such as driveways and sidewalks during the summer heat.

Crabgrass turns purple with the onset of cooler fall nights.