Spear (or Scotch) Thistle

What is spear thistle?

(Cirsium vulgare)
Spear thistle flower, photo: K. Fenner
Spear thistle is a pasture weed.

How to identify spear thistle

  • Spear thistle is an annual (living for one year) or biennial (living two years) herb, growing to 60 to 120 cm, and occasionally to 1.5 metres.
  • The leaves are dark green, rough and hairy on the upper surface, and lighter beneath due to a dense covering of whitish hairs. Rosette leaves have spines on the margins and wart-like protuberances on the upper surface. Stem leaves are divided into lobes, with the tip of each lobe ending in a spine. The stems are winged and spined and are covered with hairs. The root is a branched tap root.
  • Spear thistle flowers are reddish to purple. The flower heads are surrounded by a large number of spiny bracts, and occur singly or in groups of two or three heads at the ends of branches.
  • Spear thistle seeds germinate mainly after autumn rains. The plant over-winters as a rosette (a whorl of leaves close to the ground); rosettes grow rapidly through spring and can reach a diameter of 60 cm.
  • The rosette may produce stems, flower and die in their first summer. Alternatively, rosettes may persist through summer and continue growth into a second autumn and winter. Dead plants often remain standing for several years.
  • For help in identifying thistles in Tasmania, see Identifying Thistles in Tasmania and search the Dennis Morris Weeds and Endemic Flora database for spear thistle illustrations. If you are still in doubt about the thistle you are dealing with, contact your Regional Weed Management Officer on 1300 368 550 for help.

Spear thistle rosette, photo: K. FennerSpear thistle flower heads, photo M. Baker
Image top: Spear thistle flower, photo: K. Fenner; images above, left to right: Spear thistle rosette photo: K Fenner; Spear thistle flower heads, photo: M. Baker.

Spear thistle in Tasmania

  • Spear thistle is not declared in Tasmania.
  • Spear thistle is found in all settled parts of Tasmania, but is more common in the lower rainfall areas. Heavy infestations occur in the Midlands in some seasons, depending on rainfall, grazing pressure and soil fertility.
  • Heavy spear thistle infestations in pasture suppress pasture growth, and can virtually exclude grazing stock, leading to pasture grasses becoming rank and vulnerable to insect pests.
  • Thistle spines in the fleece of sheep can cause difficulties at shearing.

Detailed management and control guidelines for spear thistle can be found in the Spear Thistle Control Guide. Refer also to Herbicides for Spear Thistle Control. For further information see DPIPWE's Weed Links and Resources.

See also:

Spear Thistle Control Guide
Herbicides for Spear Thistle Control
DPIPWE Weed Links and Resources

Other useful links:

Pest Genie

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