What is Crabgrass?

Crabgrass is a warm season annual weed. It flourishes in direct sunlight on disturbed sites and agricultural areas. Smooth crabgrass (Digitaria ischaemum) is often found in residential and commercial areas mixed with turf. Like most weeds, it is opportunistic and it will take over your lawn - if you let it. Identification

Crabgrass is most visible during summer months. Crabgrass gets its name from the way stems grow and extend from the roots, like crab legs. Crabgrass grows in light green clumps close to the ground. Despite its distinctive growth pattern and color, it is commonly incorrectly identified.  For many, the name crabgrass is simply synonymous with the word weed.

Management: During cold weather, visible shoots will die - but not before the plant has produced seeds to ensure the long-term survival of the species.  In the spring, apply a pre-emergent herbicide formulated to fight crabgrass to your yard. Focus on areas of previous crabgrass infestation to discourage new seasonal growth.

In place of the crabgrass, install plugs or sod that is well-adapted to your area. Do not allow bare spots to remain or crabgrass will quickly re-invade.  Crabgrass thrives in sunny areas that receive shallow irrigation.  Irrigate your lawn less frequently but deeply to encourage the establishment of grass roots. Allow your grass to grow a little higher during the summer to shade out crabgrass seeds. In the long term, the best way to stop crabgrass is to replace it with properly maintained, healthy and vigorous grass.

References:
Is Crabgrass Bad?
American Lawns: Crabgrass
The Scotts Miracle-Gro Company: Crabgrass