Skip to content.
Français

Some features of this website require Javascript to be enabled for best usibility. Please enable Javascript to run.

Ministry of Agriculture, Food and Rural Affairs

Crabgrass - smooth/large

There are 2 types of crabgrass common in Ontario, smooth and large crabgrass.

Scientific Name: Smooth crab grass, Digitaria ischaemum (Schreb) Muhl, Large crabgrass Digitaria sanguinalis (L.) Scop.

Other Names: Smooth crabgrass is also called DIGIS, digitaire astringente, Finger grass, Small crab grass, digitaire glabre. Large crabgrass is also called digitaire sanguine, Finger grass, Hairy crabgrass, digitaire pourpre, panic sanguin

Family: Grass Family (Gramineae)

General Description: Annual, reproducing only by seed.

Habitat: Both kinds of crab grass are common in southern Ontario but they also occur sporadically in northern and north-western Ontario. Both occur in row crops and other fields, waste places, gardens and lawns.

Seedlings

  • The first leaf blade is lance-shaped to linear
  • Large crabgrass seedlings are upright
  • Leaves are rolled in the bud
  • No auricles
  • Jagged membranous ligule
  • Stiff hairs on the blade and sheath

Stems

Smooth Crabgrass Large Crabgrass
  • Usually shorter than large crabgrass
  • Elongated stems root at the nodes
  • 5- 20 cm (2 in.-4 ft) long
  • Erect
  • Spreading, or lying on the ground and rotting at nodes in contact with the soil

Leaves

Smooth Crabgrass Large Crabgrass
  • Smooth, hairless blades
  • Upper leaf sheaths usually smooth and hairless; lower sheaths may be somewhat hairy
  • Tuft of long hair on either side of the leaf-base of the lower leaves
  • Ligule is membranous
  • Numerous near the base, scattered along the stems
  • 4- 20 cm (1 ½ - 8 in.) long, 5- 10 mm (1/5- 2/5 in.) wide
  • Gradually tapered to a point
  • Blades and sheaths sparsely to densely soft-hairy
  • Sheaths split
  • Margins are hairless and overlapping
  • Ligule is membranous

Flowers

Smooth Crabgrass Large Crabgrass
  • Inflorescence finger-like with one thin, slender spike in a whorl at the top of the stem
  • Each spike is flattened and arranged along only one side
  • Seeds are purplish-green and ridged lengthwise
  • Flowers from August to September
  • Inflorescence finger-like with several slender spikes in a whorl at the top of the stem
  • Each spike is flattened and arranged along only one side
  • Seeds are purplish-green and ridged lengthwise
  • Flowers from July to September

Often Confused With
Goosegrass (Goosegrass is similar in overall growth habit, but goosegrass’ leaves are folded in the bud, crabgrass’ are rolled).
Southern Crabgrass (Southern crabgrass has hairs on the sheaths but lacks hairs on the blades and is only common in the south-eastern Untied States).
Dallisgrass Seedlings (Unlike crabgrass, dallisgrass has rhizomes and the leaves of the more mature plant lack hairs).

Mature crabgrass Large crabgrass. A. Plant. B. Leaf-base. C. Side view. D. Back view of a portion of spike with several spikelets. Stem and leaf-base characteristics of a typical grass Crabgrass
Click to enlarge.