Spear thistle (Cirsium vulgare)
Also known as:
black thistle
Spear thistle is an annual plant that is often mistaken for Scotch thistle. It is common throughout Australia.
Profile
How does this weed affect you?
Spear thistle is mainly a weed of agricultural areas and wasteland. It competes with sown species, inhibits livestock movement and causes both fault in wool and physical injury to animals.
What does it look like?
Spear thistle is an upright herb up to 1.5 m tall. It may be annual, biennial or a short lived perennial. At first it grows as a rosette (a cluster of leaves close to the ground growing out from a central point), as it matures it produces upright branched spiny stems.
Leaves are dark green, rough and hairy on top and white and ‘woolly’ underneath. The rosette leaves at the base of the plant are up to 30 cm long. Stem leaves are 4–25 cm long and stalkless, forming a wing down the stem.
Flowerheads are reddish to purple and 1.2 to 4 cm wide. The seeds have a tuft of soft hairs (pappus) 2–3 cm long.
Where is it found?
Spear thistle grows on the NSW coast, tablelands and western slopes, and in the Riverina. It is less common in drier inland areas. It prefers cool temperate regions, full sun and fertile, heavy clay soils.
It is native to northern Africa, Europe and Asia.
How does it spread?
By seeds
Individual plants can produce up to 8000 seeds per year. Seeds mostly sprout in autumn but may sprout other times when there is enough moisture in the soil. Seeds are spread by:
- wind (though usually not very far)
- moving water
- sticking to animals, boots, vehicles or machinery
- in hay and seed.
References
Auld, B. A., Mead, E., & Medd, R. W. (1987). Weeds: an illustrated botanical guide to the weeds of Australia. Elsevier.
Harvey, K.J., McConnachie, A.J. Sullivan, P. Holtkamp, R. and Officer, D. (2021). Biological control of weeds: a practitioner's guide for south east Australia. New South Wales Department of Primary Industries, Orange.
Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.
PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 30 August 2021 from https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Cirsium~vulgare
Sindel, B. M. (1996). Overview of thistle management in Australia. Plant Protection Quarterly, 11, 285-289.
More information
Control
Physical removal
By hand
It is best to dig out plants when they are young because they develop deep taproots.
Cultivation
Cultivation can be effective if done when plants are at the seedling or rosette stage. Do not cultivate seeding plants as this will spread the seeds.
Pasture management
Maintaining vigorous competitive pastures, especially in autumn can limit the number of seedlings that survive.
Grazing
Goats will eat thistle flowers and therefore reduce seed production.
Biological control
Three biological control agents have been released in Australia for spear thistle:
- Spear thistle gall fly(Urophora stylata), which can reduce the number of seeds per flowerhead by up to a third.
- Spear thistle receptacle weevil (Rhinocyllus conicus)
- Spear thistle rosette weevil (Trochosirocalus horridus)
All three biological control agents have established and are suitable for redistribution. The extent of their distribution and impacts is not known yet.
Contact your local weeds officer for information about biological control for this weed.
Herbicides
Apply herbicides to actively growing plants. See label for the best stage of the plant to apply the herbicide.
Herbicide options
WARNING - ALWAYS READ THE LABEL
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au
See Using herbicides for more information.
2,4-D amine 625 g/L
(Various products)
Rate: 1.1–1.6 L/ha
Comments: Boom spray. For pastures not containing legumes. Spray young rosettes.
Withholding period: 7 days withholding for grazing
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate
2,4-D LV ester 680g/L
(Estercide® Xtra)
Rate: 1.15 to 2.1 L per hectare
Comments: Boom spray application, from seedling to rosette stage
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate
Fluroxypyr 140 g/L + Aminopyralid 10 g/L
(Hot Shot™ )
Rate: 500 mL in 100 L of water
Comments: Hand gun application to actively growing plants
Withholding period: Not required for pastures when used as directed. Do not graze or cut crops for stock food for 7 days after application. See label for export restrictions.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate
MCPA 500 g/L
(Various products)
Rate: 1.5–2.0 L/ha
Comments: Boom spray. Apply to rosettes actively growing; use higher rate on larger plants.
Withholding period: Do not graze or cut for stock food for 7 days after application.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate
Picloram 100 g/L + Triclopyr 300 g/L + Aminopyralid 8 g/L
(Grazon Extra®)
Rate: 150 mL in 100 L of water
Comments: Foliar application from rosette to flowering plants
Withholding period: Where product is used to control woody weeds in pastures there is a restriction of 12 weeks for use of treated pastures for making hay and silage; using hay or other plant material for compost, mulch or mushroom substrate; or using animal waste from animals grazing on treated pastures for compost, mulching, or spreading on pasture/crops.
Herbicide group: I, Disruptors of plant cell growth (synthetic auxins)
Resistance risk: Moderate
Biosecurity duty
The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.
| Area | Duty |
|---|---|
| All of NSW | General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable. |
For technical advice and assistance with identification please contact your local council weeds officer.
Reviewed 2018
