Turf Tips
08/04/2010

Crabgrass

Crabgrass is running rampant this year as the hot summer and more than adequate rainfall has helped to push this beast of a weed along. Crabgrass is a warm-season annual grass meaning that it thrives under hot and moist conditions. The high rainfall during germination (late April and early May) coupled with the wet and warm conditions this summer have provided perfect growing conditions for this weed. As mentioned in a recent turf tip (Summer Stress: Part I: Too hot: Why some turfgrass species look poor in summer), cool-season grasses are not growing well right now and in some cases weather, disease, and insect pressure is providing more opportunity for crabgrass to invade lawns by allowing crabgrass to either germinate or fill-in thin areas of turf due to lack of competition from the desirable turfgrass.
There are many species of crabgrass, but the two most common species in lawns are smooth crabgrass (Digitaria ischaemum) and large or hairy crabgrass (Digitaria sanguinalis). Both are spreading summer annual grasses with a rolled vernation.  Large crabgrass will have a hairy stem and leaves (A) and smooth crabgrass will lack the hairs except for a few hairs at the collar region near the membranous ligule (B). Otherwise, both are fairly similar in appearance. Both are opportunistic weeds and will germinate in bare soil areas (C) or thin turf (D). When plants begin to tiller they often form clumps (E) although they are stoloniferous and can spread.

Crabgrass is especially problematic when:

What should you do now:

 


Aaron Patton, Turfgrass Extension Specialist


Send corrections, suggestions, and comments to biehlj@purdue.edu