WSU Extension

Hortsense

Weeds : Crabgrass : Digitaria spp.
(revision date: 8/13/2015)

Family: Poaceae (Graminae)
Cycle: Annual
Plant Type: Grass

Use Integrated Pest Management (IPM) for successful weed management.

Biology
Large crabgrass (Digitaria sanguinalis) may reach up to two feet tall but is often prostrate. Stems lying along the ground may root, forming mats. The flat leaf blades are relatively broad (1/4 to 1/2 inch wide), two to five inches long, and sometimes hairy. Leaf sheaths are hairy and often purplish, and auricles are absent. Ligules, which are found around the stem at the junction of the leaf blade and leaf sheath, are membranous, tall, and have jagged edges. Smooth crabgrass (D. ischaemum) is similar to large crabgrass in habit, but leaves are more slender and are not as hairy. This species is prostrate and may form mats. Seeds of both species are borne on slender, finger-like whorls of spikes two to six inches in length. They resemble Bermudagrass (Cynodon dactylon) seed heads, but crabgrass seed spikes do not all arise from one junction at the top of the stem.
Habitat
Crabgrasses are weedy in waste places, cultivated areas, lawns, and other sites, commonly on light soils.

Management Options

Non-Chemical Management
  • Cultivation (rototilling or hoeing) will effectively eliminate plants.
Select non-chemical management options as your first choice!

Chemical Management

Summer annual grasses are rarely a problem in western Washington; no herbicides are recommended. In lawns, keeping the grass dense to crowd out crabgrass is the best defense. Cultivation in lawns is not a practical option. Conversely, preemergent herbicides are very effective in controlling crabgrass in eastern Washington; apply in spring when soil temperatures reach 50 to 55 degrees F. (usually about the time forsythia bloom). There are several postemergent products, which can be applied by a licensed professional for control. Glyphosate and glufosinate products should be applied as spot treatments only! NOTE: Some ingredients listed here are only available in combination. Read the label carefully on combination products to make sure the product is suitable for your specific situation.

Landscape areas
  • glyphosate
  • dichlobenil
  • glufosinate
  • trifluralin
  • sethoxydim
  • fluazifop
Turf areas
  • products containing benefin
  • pendimethalin
  • benefin, trifluralin
Bare ground areas
  • glyphosate
Images
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Caption: Crabgrass
Photo by: R. Parker
Caption: Line drawing of crabgrass
Photo by: Ciba Geigy
Caption: Multiple crabgrass seed heads
Photo by: T.W. Miller
Caption: Crabgrass hairy leaves
Photo by: T. W. Miller
Caption: Crabgrass seedheads
Photo by: T. W. Miller