Onion weed control guide

Do's and Don'ts of onion weed control

Onion Weed - flowering plant


  • Plan your control program, this will save time and money in the long-run;
  • Consider the impact of your control methods on off-target species, especially if herbicides are used;
  • Ensure machinery and equipment is washed down between sites or prior to contractors leaving site;
  • Get in early - For new infestations, eradicate before the plants reach the flowering stage: once plants begin seeding, control becomes more difficult and expensive;
  • Carefully time your use of herbicide for best results (see the Herbicides for Onion Weed Control link for more information);
  • Coordinate your control program with neighbouring landholders where your weed problem crosses property boundaries;
  • Revisit and regularly inspect the site and ensure follow-up is undertaken;
  • Use a combination of different control methods; and
  • Establish vigorous pasture (or native species) after removal to reduce re-infestation.


  • Don't introduce onion weed to onion weed-free areas (e.g. by failing to wash down machinery and equipment between sites);
  • Don't start your control program without first planning your approach;
  • Don't allow onion weed to flower and set seed before treatment;
  • Don't rely on one attempt at removal - follow-up is essential;
  • Don't rely on just one control method

Spread of onion weed

  • Spread of onion weed is by seed.
  • Onion weed seed can be spread by water, on wool and clothing, in produce, and on vehicles and farm machinery.
  • Seed on dead plants can be spread during cultivation when the plant is dragged along by machinery, or when the dead plants are blown about by the wind.
  • Seeds can remain viable in the soil for many years.
  • See the Washdown Guidelines for Weed and Disease Control for detailed information on how to wash-down equipment and personnel to reduce the chance of spreading onion weed.

Physical removal

  • Single plants and small infestations can be removed by hand-pulling or hoeing. Remove plants before seeding.
  • Larger infestations should be controlled by cultivation or establishing a vigorous legume pasture.


  • Onion weed is readily killed by cultivation as it does not have rhizomes or tubers from which plants can regrow.
  • If plants are cut below the soil surface they will die. However, plants which are only partly turned over during cultivation can survive, particularly when the soil is moist.
  • Cultivation may not be feasible on more arid sites where the weed occurs. A suitable program can be to cultivate in summer when the soil is dry to kill existing plants, cultivate in a second summer, and then plant a cereal crop under-sown with lucerne in early winter. Avoid grazing the lucerne in the first year.
  • On non-arable land, sow with legume pasture to compete with germinating onion weed seedlings.

Chemical control

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