Grains Research and Development


Doublegee (Emex australis)

Mature doublegee plant with flowers and fruits
Mature doublegee plant with
flowers and fruits
(Photo A. Storrie)

Doublegee or three corner jack (Emex australis) is a vigorous annual weed with a strong tap root and a long, fleshy, hairless stem. The cotyledons are hairless, elongated and club-shaped. Subsequent leaves are alternate, hairless and triangular with undulating margins.

Ovate leaves form a prostrate rosette at early stages of growth but can assume a semi-erect habit in dense crop or pasture.

Round, ribbed stems branching from the centre of the rosette may grow up to 600 mm in length. Clusters of very small, inconspicuous white flowers produce hard woody achenes with three sharp spines radiating from the apex.

Factors that make doublegee a major weed:

  • Competes against crops and reduces yield
  • Produces a large number of seeds
  • Can contaminate grain, leading to a rejection of grain deliveries
  • Seed dispersal in agriculture is diverse
  • Can cause animal health problems
  • Has evolved resistance to herbicides

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.