Ontario Weeds: Smooth crab grass

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Name
  2. Other Names
  3. Family
  4. General Description
  5. Stems and Roots
  6. Flowers and Fruit
  7. Habitat
  8. Similar Species
  9. Related Links

Name: Smooth crab grass, Digitaria ischaemum (Schreb) Muhl.

Other Names: DIGIS, disitaire astringente, Finger grass, Small crab grass, digitaire glabre

Family: Grass Family (Gramineae)

General Description: Before heading out, both Smooth crab grass and Large crab grass are distinguished by their tapered leaf blades, their split sheaths with hairless margins, their membranous ligueles with no auricles, their more or less hairy lower leaf sheaths adn their either hairy or smooth blades. After heading out, the slender finger-like spikes are distinctive.

Photos and Pictures

Smooth crab grass. Viewed from above.
Smooth crab grass. Viewed from above.

Stem and leaf-base characteristics of a typical grass.

Stem and leaf-base characteristics of a typical grass.

Stems & Roots: Smooth hairless leaf blades, and upper leaf sheaths usually smooth and hairless, but the lower ones may be womewhat hairy; ligule also membranous but usually a bit longer (2-3mm, 1/12 - 1/8in.), nad there is a tuft of long hair on either side of the leaf-base of the lower leaves.

Flowers & Fruit: No auricales; inflorescence almost identical to that of Large crab grass but usually with only a single whorl of spikes at the end of the stem. Flowers from August to September.

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

Similar Species: Very similar to Large crab grass but is usually shorter.

Related Links

... on general Weed topics
... on weed identification, order OMAFRA Publication 505: Ontario Weeds
... on weed control, order OMAFRA Publication 75: Guide To Weed Control

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