Nodding Thistle: State Prohibited Weed
Nodding thistle, Musk thistle
Carduus nutans L.
Nodding thistle is declared under the Catchment and Land Protection Act (1994) as a State prohibited weed.
State prohibited weeds either do not occur in Victoria, or are present and can reasonably be expected to be eradicated. State prohibited weeds are the highest category of noxious weeds under the Catchment and Land Protection Act (1994). The Department of Economic Development, Jobs, Transport and Resources (DEDJTR) is responsible for the eradication of State prohibited weeds. The Victorian Government is committed to preventing the introduction of high-risk weeds into Victoria, to protect our environment and economy.
Nodding thistle has its origins in Europe, North Africa, Asia Minor and Asia. It came to Australia as a contaminant of seed from New Zealand before 1950.
Nodding thistle is an erect annual, or usually biennial, and occasionally triennial herb, most often 80 to 120 cm high. It usually has a single stem which branches in the upper half, but may become multi stemmed if the crown is damaged. Plants exist as a rosette before the stem elongates.
Stems - erect, grooved, slightly downy with spiny wings from the base of leaves to below the flower heads; up to 150 cm tall.
Leaves - rosette leaves up to 50 cm long, spiny and pressed to the ground and becoming deeply lobed into the whitish midvein. Each lobe ends in a spine about 3 mm long and lobes often have a whitish margin. Stem leaves up to 40 cm long, deeply lobed to the midvein, hairy, with rigid spines.
Flowers - pink, red, purple, mauve or rarely white; formed in solitary woolly heads, up to 6 cm diameter, at the ends of branches; flower heads at first upright but distinctively drooping at right angles to the stem when mature. Each flower head is surrounded by many purplish bracts which terminate in a sharp rigid spine. Individual flowers are 4 to 8 mm across.
Seeds - 3 to 4.5 mm long with lines from end to end and faint dots; slightly curved, shiny, finely wrinkled and grey to yellowish brown. There is a rim at one end with a conical tip to which fine white bristles 15 to 25 mm long are attached. This pappus is easily separated from the seed.
Figure 1: Nodding thistle.
Roots - substantial branched taproot down to 40 cm or more deep.
Seed germination is usually from late summer to early winter and flowering occurs from spring through summer to autumn. Some germination may occur in spring and early summer. These plants remain in the rosette stage until their second spring when they shoot up a main stem and flower, thus acting as biennials.
Seed is the only means of reproduction. It may be carried as a contaminant of produce seed and hay, on vehicles and machinery, and in water and soil. Because the pappus easily separates from the seed, wind does not have a major role in dispersal and seed are usually not blown more than 10 m.
Nodding thistle is not readily grazed and the large size of the plants can quickly prevent stock access to pastures. Because the main germination period is late summer and early autumn nodding thistle can invade fertile annual pastures as the favoured pasture species die off. Nodding thistle infestations have been recorded in the eastern part of Victoria.
What should you do if you find an nodding thistle plant?
If you think you have purchased or seen an alligator weed plant, please contact DEDJTR by telephoning 136 186 or use the online reporting tool.
Please do not attempt to control or dispose of this weed yourself.
Parsons, W.T. and Cuthbertson, E.G. (1992) Noxious Weeds of Australia. Melbourne, Inkata Press.
Popay, A.I. and Medd, R.W. (1995) Carduus nutans L. ssp. nutans. Pp. 29-49 in Groves, R.H., Shepherd, R.C.H. and Richardson, R.G. (Eds.) The Biology of Australian Weeds Volume 1. Melbourne, R.G. and F.J. Richardson.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.