Carduus pycnocephalus L.
Slender Thistle

Sp.Pl. Ed.2,2:1151 (1763)
Conservation Code
Not threatened
Naturalised Status
Alien to Western Australia
Name Status

Erect, prickly annual, herb, 0.2-1 m high. Fl. purple-pink-red, Oct to Dec. Weed of roadsides & pastures.

Amanda Spooner, Descriptive Catalogue, 23 April 1997


IBRA Regions
Avon Wheatbelt, Coolgardie, Esperance Plains, Jarrah Forest, Mallee, Swan Coastal Plain, Warren.
IBRA Subregions
Fitzgerald, Katanning, Mardabilla, Northern Jarrah Forest, Perth, Recherche, Southern Jarrah Forest, Warren, Western Mallee.
IMCRA Regions
Leeuwin-Naturaliste, WA South Coast.
Local Government Areas (LGAs)
Albany, Armadale, Boyup Brook, Bridgetown-Greenbushes, Busselton, Cambridge, Capel, Chittering, Denmark, Dumbleyung, Esperance, Gingin, Harvey, Jerramungup, Kondinin, Manjimup, Murray, Nannup, Nedlands, Northam, Plantagenet, Rockingham, Serpentine-Jarrahdale, Toodyay, Wanneroo, Waroona, York.

Management Notes (for the Swan NRM Region)

Alternative Names. Italian Thistle, Plymouth Thistle, Shore Thistle.

General Biology. Growth form. Herb. Life form. Annual. Reproduction. Seed. Dispersal. Wind, water, birds. Toxicity. Potentially toxic to stock due to nitrates. Seedbank persistence. 10+ years.

Notes. Can form a dense cover that reduces establishment and diplaces other plants. Prefers fertile soils. Germination generally occurs 4-6 weeks following autumn rains and is not staggered. Seed germinates rapidly, generally on open bare ground, and at high rates at a range of alternating temperatures. Produces two types of seed in each flower head. Those in the centre are not dormant and are easily dispersed by wind due to a large pappus, while the outer seed can be dormant and have no obvious means of dispersal. A biological control program tested two agents, a weevil and rust fungus. Hybridisation with Carduus tenuiflorus is common. Declared plant in Victoria, South Australia and Tasmania.

Additional information. Origin. Macaronesia, temperate Asia, tropical Asia, Europe. Similar exotic species. Carduus tenuiflorus.

Suggested method of management and control. Hand remove isolated plants through spring and early summer. Glyphosate at 50% applied by wick or spot spraying with 0.5% glyphosate provides good control. Alternatively spot spray Lontrel® 10 ml/10 L + wetting agent. Best controlled at rosette stage. An integrated program involving a combination of techniques will be most effective. Read the manufacturers' labels and material safety data sheets before using herbicides. For further information consult the Australian Pesticides and Veterinary Medicines Authority to determine the status of permits for your situation or state.

Management Calendar

Calendar Type Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Comments
Germination         O Y Y            
Active Growth           Y Y Y Y Y Y    
Flowering                   Y Y Y  
Fruiting Y                     Y  
Manual Removal Y               Y Y Y Y  
Herbicide Treatment             Y Y Y Y Y    

Legend: Y = Yes, regularly, O = Occasionally, U = Uncertain, referred by others but not confirmed.



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