Darrell Blackwelder: Crabgrass thrives in hot weather

Published 12:00 am Saturday, August 5, 2023

Crabgrass is running rampant in our cool-season fescue lawns and shrub beds. The grassy weed is a warm season annual that thrives in hot weather experienced over the past few weeks. It is an endogenous weed that can adapt 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 mowing too closely produces weak stands of fescue in the heat of the summer.

Crabgrass is a clump grass, similar to fescue, but with a faint, blue colored leaf blades. A single crabgrass plant produces thousands of minute seed which can remain dormant in the soil for years. It’s such prolific grass, scientists have tried to produce a type that could be planted as a lawn grass. Unfortunately, the grass seed does not germinate quickly and could not be developed as a grass for lawns.

Crabgrass is best controlled with preemergence herbicides in early spring or with post emergence herbicides later after the grass has emerged. Unfortunately, it is too late to control crabgrass with preemergence herbicides. Crabgrass dies out completely at the first hard frost. Dead plants should be raked and over-seed with fescue to fill the void in early fall. Glyphosate or herbicides 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 is the retired horticulture agent with the North Carolina Cooperative Extension Service in Rowan County. Contact him at deblackw@ncsu.edu.

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