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Ministry of Agriculture, Food and Rural Affairs

smooth crab grass

Scientific Name: Digitaria ischaemum

Other Names: Finger grass, small crab grass, distaire astringente, distaire glabre

Family: Grass Family (Gramineae)

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

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


Stems

  • Stems are erect
  • Stems can reach a length of 5 -120 cm
  • Stems can be spreading or lying on the ground and rooting at nodes

Leaves

  • Leaves are smooth and have hairless leaf blades
  • Upper leaf sheaths usually smooth and without hair
  • Lower leaf sheaths may be somewhat hairy
  • Ligule is also membranous
  • Tuft of hair on either side of the leaf-base of the lower leaves
  • No auricles

Flowers and Fruit

  • Almost identical inflorescence to that of large crab grass
  • Only has a single whorl of spikes at the end of the stem
  • Flowers from August to September

Often Confused With / Distinguishing Features
It is often confused with large crab grass and fall panicum. It is distinguished by tapered leaf blades, membranous ligules without auricles and hairy lower leaf sheathes. It is distinguished from large crab grass by only having a single whorl of spikes at the end of the stem.

Herbicide Resistance

There are no documented cases of herbicide resistance to date.

References

www.weedinfo.ca/en/weed-index/view/id/DIGIS

www.omafra.gov.on.ca/english/crops/facts/
ontweeds/smooth_crabgrass.htm

 

Membranous ligule of smooth crab grass Leaf blade of smooth crab grass that is smooth (hairless) on both sides Leaf sheath of smooth crab grass that are also hairless Smooth crab grass seed headMature smooth crab grass plantClick to enlarge.