|Common name:||perennial thistle|
|Scientific name:||Cirsium arvense (L.) Scop.|
|Other scientific name/s:|
|Other common name/s:||Californian thistle|
Catchment management authority boundaries
Regionally prohibited in the North Central and North East Catchments
Regionally controlled in the Glenelg Hopkins, Goulburn Broken, Wimmera, Corangamite, West Gippsland, East Gippsland, Port Phillip and Western Port Catchments
Restricted in the Mallee Catchment
Shrub (or bush)
Californian thistle is an erect perennial herb growing to 50 cm high.
Stems are ridged and plants have multiple stems which branch near the top of the plant.
Leaves are alternately arranged and the shape varies from oblong to lance-shaped.Californian thistle leaves are toothed or lobed with wavy, spiny margins. They are white and woolly on the underside and grow to 15 mm long.
Flower colour ranges from red-purple to pink. They are 15-25 mm long and surrounded by layers of purplish, almost spineless modified leaves that are enclosed by green bracts.
Male and female flower heads are on separate plants.Californian thistle flowers during summer.
Fruit of the Californian thistle is light brown to olive green, smooth and shiny with a ring of deciduous white hairs.
Growth and lifecycle
Method of reproduction and disperal
The plant is mainly dispersed via its spreading root system.
Roots may be fragmented during cultivation and can be easily spread onto clean land.
The seed of the Californian thistle is easily dispersed by wind and water and readily contaminates machinery and farm equipment.
Rate of growth and spread
Californian Thistle is a perennial plant and grows in summer, browning-off over the colder months.
Infestations have been known to increase in size, expanding outwards by up to 13 metres in a single year from rhizome growth alone.
Any soil cultivation and movement may transfer rhizome fragments to new areas, resulting in new infestations.
Seedbank propagule persistence
Californian thistle rarely produces fertile seed as the plant's female flowers require the presence of male flowers within approximately 100 metres to allow for successful insect pollination.
Viable seed may be more frequently produced now that the weed is more abundant.
Californian thistle prefers subhumid to humid, cool temperate regions where it occurs in open, moderately-warm situations up to sub-alpine levels.
In Australia, it is generally confined to pastures, cultivated crops, roadsides and neglected sites. Although it is more vigorous in the wetter areas where rainfall exceeds 750 mm, Californian thistle is capable of growing in drier areas and can adapt to most soil types.
Californian thistle is a problem mainly in southern Victoria, occurring commonly throughout Gippsland and the Western District.
The icons on the calendar below represent the times of year for flowering, seeding, germination, the dormancy period of Perennial thistle and also the optimum time for treatment.
Agricultural and economic impacts
Californian thistle is a very competitive weed in cropping areas.
The plant also interferes with harvesting operations.Infestations in grazed areas are rarely eaten by stock due to the weed's sharp spiny leaves.
Prescribed measures for the control of noxious weeds
- Application of a registered herbicide
- Physical removal
Other management techniques
Changes in land use practices and spread prevention may also support perennial thistle management after implementing the prescribed measures above.
Parsons, W.T. and Cuthbertson, E.G. 2001, Noxious weeds of Australia, 2nd edn, Inkata Press, Melbourne & Sydney.
Department of Primary Industries, Regionally Prohibited Weed Information Sheet - Californian Thistle, 2010.