Darrell Blackwelder: Crabgrass thrives in hot weather

Published 12:00 am Sunday, August 4, 2019

Crabgrass is running rampant in our cool season fescue lawns and shrub beds.

It is a warm season, annual grass that thrives in the hot weather we’ve experienced over the past few weeks.

Crabgrass is an endogenous weed [having an internal cause or origin], easily adapting to both wet and dry summer conditions of the Piedmont. It is normally the first grass in early summer to invade thin or weak fescue lawns.

Fertility problems, fungal diseases and fescue mowing too closely produces weak stands of fescue in the heat of the summer.

Crabgrass grows as a clump grass, similar to fescue, but with a faint, blue colored leaf blades. A single crabgrass plant produces thousands of minute seeds which can remain dormant in the soil for years.

Crabgrass is best controlled with preemergence herbicides in early spring or with post emergence herbicides during the early summer. It is too late to control crabgrass with preemergence herbicides.

Crabgrass dies out completely at the first hard, killing frost. Dead plants should be raked and over-seed with fescue to fill the void in early fall.

Glyphosate or herbicides such containing diquat quickly kills spots of crabgrass clumps.

Go to https://www.turffiles.ncsu.edu/weeds-in-turf/large-crabgrass/ for more detailed information on crabgrass control.


Darrell Blackwelder deblackw@ncsu.edu is the retired horticulture agent with the North Carolina Cooperative Extension Service in Rowan County.