Grains Research and Development

Paradoxa grass

Paradoxa grass (Phalaris paradoxa)


Paradoxa grass seedlings
(Photo A. Storrie)

Paradoxa grass (canary grass) (Phalaris paradoxa) is an invasive, tufted, annual grass capable of producing a large number of tillers. It generally thrives in moist conditions growing to a height of 1.2 m. Paradoxa grass has distinct reddish purple colouring at the base of the stems and also around the nodes.

The leaf blade is flat, hairless and approximately 200 mm long. As with many grass species, identification during the vegetative stage is reliant upon correct recognition of the ligule and auricle characters. The ligule is translucent and thinly membranous, and there are no auricles. The seed-head is readily distinguishable although there is variation in the spikelet cluster.

Factors that make paradoxa grass a major weed:

  • The success of paradoxa grass is attributable to its competitiveness and its ability to produce large numbers of seeds
  • Can cause staggers in sheep
  • A contaminant of winter cereals and may lead to reduced returns
  • Seed heads tend to shatter when disturbed and drop seed in windy conditions
  • Herbicide resistance is known
  • Thrives in a poorly competitive crop

Further detail about this weed including integrated weed management tactics that could be considered when developing a management plan can be found in the section on problem weeds in the Integrated Weed Management Manual.

Further information

Ecology and biology of common weeds are outlined in section 6 of the Integrated Weed Management Manual.  

Other information

Dynamics of  paradoxa grass (Phalaris Paradoxa L.) soil seedbank. (1999), I. Taylor et al. Twelfth Australian Weeds Conference (CAWS) 

Managment of wild oats and paradoxa grass with reduced dependence on herbicides (1998)  S. Walker et al. Ninth Australian Agronomy Conference