Amsinckia Species (Yellow Burrweeds)

Amsinckia, photo: Karen Stewart

What is Amsinckia?

  • Amsinckia species are erect annual herbs from the Americas, also known as yellow burrweeds or fiddlenecks. There are four species of amsinckia naturalised in Australia, A. calycina is known in Tasmania.
  • Amsinckia is a significant crop weed in Tasmania.
  • Amsinckia species are declared weeds in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of amsinckia are prohibited in Tasmania.

How to identify Amsinckia

  • Amsinckias are hairy, winter-growing annual herbs, usually 20 to 70 cm high.
  • Seeds germinate with the first autumn rains and further germinations occur through autumn and winter. The plant grows as a rosette (a whorl of leaves close to the ground) during winter and a flowering stem emerges in late winter or spring.
  • Small yellow trumpet-like flowers are arranged along one side of the stem in a spike-like inflorescence coiled at the top. Flowering occurs from August to October/November. Aromatic seeds replace the small flowers in summer and autumn. Plants die off after seed set.
  • For further help in identifying amsinckia, search the Dennis Morris Weeds and Endemic Flora database for amsinckia illustrations. If you are still in doubt about the weed you are dealing with, contact Biosecurity Tasmania on 03 6165 3777 for help.
Amsinckia, photo: Karen Stewart
Photo top: Amsinckia - flowering, © Karen Stewart
Photo above: Amsinckia close-up, © Karen Stewart

Amsinckia in Tasmania

  • Amsinckia occurs in southern and northern Tasmania, particularly in the Derwent Valley and Central Highlands. Amsinckia grows in a wide range of soil types and climates, but prefers disturbed, dry and open situations.
  • Amsinckia is a weed of grain, poppies and other crops, and is also found in poorly managed pastures and along roadsides. Prolific and staggered seeding makes amsinckia a very competitive weed and heavy infestations can cause large yield losses. Amsinckia seed can contaminate grain, and the bristly flowers can contaminate wool.
  • Bristles on the leaves and stems make the plant unattractive to stock and it is generally unpalatable. At least one species of amsinckia is toxic to stock, causing liver damage and increased sensitivity to light, with cattle, horses and pigs being most susceptible.

What is the legal status of Amsinckia in your area?

  • The legal responsibilities of landholders and other stakeholders in dealing with amsinckia are laid out in the Amsinckia Statutory Weed Management Plan.
  • Use Table 1 (Zone A municipalities) and Table 2 (Zone B municipalities) in the Statutory Weed Management Plan to find out whether your area falls in an eradication or containment zone.
Detailed management and control guidelines for amsinckia can be found in the Amsinckia Control Guide. Refer also to Herbicides for Amsinckia Control. For further information see DPIPWE's Weed Links and Resources.

See also:
Herbicides for Amsinckia Control
Statutory Management Plan for Amsinckia
Weed Links and Resources

Other useful links:
Pest Genie

Amsinckia Control Guide


  • Plan your control program, this will save time and money in the long-run;
  • Ensure cultivation, harvesting and road-grading machinery used in an infested area is washed down to remove any amsinckia seed;
  • Maintain a dense and vigorous pasture to prevent amsinckia establishing;
  • Take careful note of stock withholding periods after spraying to avoid stock eating the treated amsinckia;
  • Seek a vendor declaration to identify weeds which may be present in purchased feed and grain;
  • Use a dedicated feedout area to avoid spread of weeds that may come in purchased feed and grain.


  • Don't introduce amsinckia into amsinckia 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 rely on slashing to remove amsinckia;
  • Don't expose stock to dense amsinckia infestations in case of poisoning.

Spread of Amsinckia

  • Amsinckia spreads by seed only. Seed is spread on farm equipment, in contaminated fodder and feed grain, and via sowing of contaminated seed. Seed can also be spread by contaminated bird seed.
  • Amsinckia can also be spread when the bristly flowers lodge in the coats of feral animals and stock, and when seed is carried in the digestive tracts of birds and stock.

Avoid the introduction of Amsinckia

  • Implements and vehicles which have been used on infested areas should be thoroughly cleaned before leaving the site.
  • Avoid using fodder and seed grain sourced from areas infested with amsinckia.
  • 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 amsinckia.

Physical removal

  • Small infestations of amsinckia can be removed by hand pulling.
  • For larger infestations on grazing land, mowing or slashing just before flowering can reduce seed production and if undertaken repeatedly will deplete the soil seedbank.


  • Amsinckia germinates over an extended period in the autumn and winter, making it very difficult to control by cultivation alone.
  • In cereal fallows, repeated cultivations will destroy amsinckia seedlings from early germinations, but follow up herbicide treatment is needed after crops are sown.
  • Repeated harrowing can be effective in controlling seedlings.
  • Competition from pasture legumes can be used to suppress amsinckia during the fallow phase on lands used for cereal growing.


  • Grazing of goats can be used to control amsinckia.

Chemical control

  • A number of herbicides are registered for use on amsinckia in Tasmania (see Herbicides for Amsinckia Control for more information).
  • Glyphosate products can be used for control in pasture or cropping situations prior to sowing.
  • Metsulfuron-methyl applied before crop is sown will give control from several germinations before and after crop.
  • Staggered seeding makes control in cropping situations challenging. For information relating to control in specific cropping situations contact an agronomist.

Herbicides for Amsinckia Control

Herbicides for Amsinckia Control

Important Disclaimer

To the extent permitted by law, the Department of Natural Resources and Environment Tasmania (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using information or material (in part or in whole) contained on this website.