Ontario Weeds: Large crabgrass

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Excerpt from Publication 505, Ontario Weeds, Order this publication

Table of Contents

  1. Scientific name
  2. Family
  3. General description
  4. Habitat
  5. Seedlings
  6. Stems
  7. Leaves
  8. Flowers and fruit
  9. Often Confused With / Distinguishing Features
  10. Herbicide Resistance
  11. Photos
  12. References
  13. Related Links

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

  • 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

Stems :

  • Stems 5-120 cm long
  • Erect, spreading, or lying on the ground and rooting at nodes

Leaves

  • 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

Flowers & Fruit:

  • Inflorescence is finger-like with several spikes in a whorl at the top of the 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.

Photos:

Figure 1: Membranous ligule of large crab grass

Figure 1: Membranous ligule of large crab grass

Figure 2: Large crab grass leaf blade which is hairy on both sides

Figure 2: Large crab grass leaf blade which is hairy on both sides

Figure 3: Leaf sheath of large crab grass which is hairy but the leaf margins are hair-less

Figure 3: Leaf sheath of large crab grass which is hairy but the leaf margins are hair-less

Figure 4: Large crab grass seed head

Figure 4: Large crab grass seed head

Figure 5: Mature plant of large crab grass

Figure 5: Mature plant of large crab grass

References

http://www.weedinfo.ca/en/weed-index/view/id/DIGSA

http://www.ipm.ucdavis.edu/PMG/WEEDS/large_crabgrass.html

Related Links

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

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For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 01 June 2000
Last Reviewed: 17 May 2013