Star Thistle

(Centaurea calcitrapa)
Star thistle, photo: CDFA 

Status of star thistle in Tasmania

  • Star thistle is a declared weed in Tasmania under the Tasmanian Weed Management Act 1999. The importation, sale and distribution of star thistle are prohibited in Tasmania.
  • The legal responsibilities of landholders and other stakeholders in dealing with star thistle are laid out in the Star Thistle Weed Management Plan.

What does star thistle look like?

  • Star thistle is an erect, bushy and spiny herb that usually lives for one (annual) or two years (biennial). Star thistle grows to 1 metre high. The young stems have fine, cobweb-like hairs that fall off over time. Older stems are much-branched, straggly, woody and sparsely hairy. The rosette leaves are much divided and do not have spines, while the stem leaves are narrow and undivided. Numerous lavender to deep purple flowers are borne on the ends of branches or in the leaf axils. The flowers are surrounded by numerous sharp, rigid, white or yellowish spines which are 1.5 to 3 cm long.
  • Most seeds germinate in autumn. Rosettes are formed in winter and spring, and flowering stems are usually produced in late spring (where the weed is an annual), but may only be produced in the second spring (biennial plants). Flowering occurs from November to February, after which the plant dies.
  • Spread is by seed. The seeds lack a tuft of hair for wind dispersal (called a pappus) and are not readily spread by wind. Most spread is by water and via contaminated agricultural produce and equipment.
Star thistle, photo: Luigi Rignanese Star thistle, photo: CDFA
Image top: Star thistle, © CDFA.
Image above left: Start thistle flowering, © Luigi Rignanese.
Image above right: Star thistle, © CDFA.

Impacts of star thistle

  • Star thistle is a weed of pasture and crops, and the spines can injure grazing animals particularly in the eyes and mouth.

Where does star thistle occur

  • Star thistle is a native of Europe, temperate Asia and North Africa. Star thistle has naturalised in all mainland States and Territories except the Northern Territory.
  • Star thistle has not naturalised in Tasmania.

What you need to do

  • If you locate star thistle anywhere in Tasmania, or if you find a plant that you think could be star thistle, immediately contact Biosecurity Tasmania on 03 6165 3777 to report this weed.

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