Crabgrass - University Of Maryland Extension

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Large crabgrass (Digitaria sanguinalis) Photo: Betty Marose

Updated: March 13, 2023

Life cycle

Large crabgrass (Digitaria sanguinalis) is a summer annual weed. It is also called hairy crabgrass.

Growth habit

Crabgrass has a prostrate growth habit; the lower stems branch out and spread across the ground, and it can grow upward to 2 feet tall. The stems have swollen nodes; plants can develop roots at the nodes and form small colonies. The leaf blades have small hairs. Roots are fibrous. Flowers have 3 to 5 or more spikes. Crabgrass dies after the first frost in the fall.

Reproduction

Crabgrass reproduces primarily by seeds, which germinate from spring through late summer when the soil temperature is above 55°F for at least 3 consecutive days.

Conditions that favor growth

Thin turf with bare spots; mowing a lawn too short will favor crabgrass.

Photos

Growth habit

Crabgrass growth habit

Photo: Bruce Ackley, The Ohio State University, Bugwood.org

Seedling

Crabgrass seedling

Photo: Rebekah D. Wallace, University of Georgia, Bugwood.org

Flower

Crabgrass flower

Photo: Rebekah D. Wallace, University of Georgia, Bugwood.org

Management in lawns

Maintain healthy, dense turf that can compete and prevent weed establishment. Mow lawn at 3-4 inches high during the growing season and seed bare spots.

Lawn Care

Mechanical management

Hand pulling or using an appropriate weeding tool to remove the roots is a viable option at the beginning of an infestation and on young weeds. Hand pulling when the soil is moist makes the task easier. Try to remove the weed without disturbing the soil.

Manage Weeds Without Chemicals

Chemical prevention/management in lawns

Apply a granular (apply with a spreader), selective, preemergent herbicide. There are numerous products on the market. Look for a preemergent without nitrogen fertilizer.

Active ingredients include bensulide, dithiopyr (which offers postemergent control on young crabgrass seedlings), pendimethalin, and prodiamine.

Rainfall or irrigation is required to dissolve the herbicide which is then absorbed into the upper portion of the soil and forms a barrier that kills weed seedlings. Preemergent grass herbicides have a residual activity that lasts for several weeks after application. High temperatures and rainfall will decrease the length of time they remain at sufficient concentration to be effective.

Tips for application

• Apply prior to seed germination. For crabgrass, this begins when soil temperatures are sustained at 53-55° for 5 days (during and shortly after, forsythia bloom is rough, but not consistently reliable, a guide for application timing).
  • Soil Temperature Maps (linking to this site does not endorse any company, manufacturer, or product by University of Maryland Extension).
• Water after application, according to the label.
• A second application may be possible, usually 6-8 weeks later (see label).
• Consult label for the specific waiting period between application and overseeding.

Spot treated actively growing crabgrass early in the season when it is young with a postemergent herbicide before it matures and goes to seed. Look for the following active ingredients: Common Name: Quinclorac; Trade Name: Drive; others, can be combined with other active ingredients, Common Name: Fenoxaprop-p-ethyl; Trade Name: Acclaim Extra, others.

Lawn Herbicides for Weed Management

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