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Ministry of Agriculture, Food and Rural Affairs

large crab grass

Scientific Name: Digitaria sanguinalis

Family: Poacaea (Grass)

General Description: Large crab grass is an annual weed reproducing only by seed.

Habitat: Large crab grass is common in southern Ontario but also found in northern and northwestern Ontario in row crops and other fields, waste areas, gardens, and lawns.


  • Seedlings are pale green and covered in coarse hair
  • Form in clumps with shallow roots
  • Young leaves are curled in a bud and unroll as they grow


  • Stem is 5 – 120 cm long
  • Erect, spreading or lying on the ground and rooting at nodes


  • Leaves are numerous at the base of the plant and are scattered along the rest of the stem
  • Leaves are 4 – 20 cm long
  • Leaves gradually taper towards a pointed tip
  • Leaf blades and sheaths are covered with soft hairs
  • Leaves have no auricles

Flowers and Fruit

  • Inflorescence is finger-like with several spikes in a whorl at the top of stem
  • Flowers from July to September

Often Confused With / Distinguishing Features
Large crab grass is often confused with smooth crab grass, proso millet and witch grass. Large crab grass seedlings often resemble witch grass seedlings but large crabgrass seedlings are covered with shorter hairs than witch grass seedlings. Large crabgrass differs from other weeds as it has no auricles, hairy leaf sheaths and their finger-like spikes are distinctive.

Herbicide Resistance

Large crab grass resistant to all WSSA Group 1 herbicides (fops and dims) has been documented in Ontario.


Membranous ligule of large crab grass Large crab grass leaf blade which is hairy on both sides Leaf sheath of large crab grass which is hairy but the leaf margins are hair-less Large crab grass seed headMature plant of large crab grassClick to enlarge.