Weed Seed: Annual vernal grass (Anthoxanthum aristatum)

Family

Poaceae

Distribution in Canada

Found in BC

Duration of life cycle

Annual

Seed/Fruit type

  • grain, enclosed by a palea and lemma
  • floret may be found enclosed in sterile florets with awns (long bristles)

Seed identification features

Size

  • floret length: 1.7–2.0 mm
  • floret width: 0.5–0.7 mm
  • enclosed floret length: 3.2 mm
  • enclosed floret width: 1.0 mm
  • awn length: 8.0 mm

Shape

  • in outline: elongated oval
  • in cross section: elliptical

Surface texture

  • enclosing (sterile) floret surface is papery and slightly roughened like sandpaper
  • short, stiff hairs surround base of enclosing floret, and run up floret in lines
  • fertile floret has smooth, glossy surface

Colour

  • medium reddish-brown, becoming pale at tip

Other structures

  • long, bent awn extends straight from tip of 2 papery, sterile florets surrounding fertile, plump floret

Similar species

Sweet vernal grass (Anthoxanthum odoratum)

  • found in YT, BC, ON, QC, NB, NS, PE, NL
  • similar to annual vernal grass in size, elliptical shape, reddish-brown colour, bent awn-tipped enclosing florets, and dense bristles
  • Sweet and annual vernal grass florets are very similar, plants are easily distinguishable by their duration and vegetative features
  • florets are slightly (~0.5 mm) larger than annual vernal grass florets
  • outer (sterile) florets are densely covered by stiff hairs (annual vernal grass hairs are in vertical lines)

Photos

Photo - Annual vernal grass (Anthoxanthum aristatum) floret group 1
Annual vernal grass (Anthoxanthum aristatum) floret group 1
Photo - Annual vernal grass (Anthoxanthum aristatum) floret group 2
Annual vernal grass (Anthoxanthum aristatum) floret group 2
Photo - Annual vernal grass (Anthoxanthum aristatum) floret groups
Annual vernal grass (Anthoxanthum aristatum) floret groups

Similar species

Photo - Sweet vernal grass (Anthoxanthum odoratum) floret group
Similar species: Sweet vernal grass (Anthoxanthum odoratum) floret group
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