Spiny biennial, herb, 0.05-1.5(-3) m high. Fl. purple-red, Jan to Dec. Weed of pastures & roadsides in higher rainfall areas.
Beard’s Provinces: Eremaean Province, South-West Province.
IBRA Regions: Avon Wheatbelt, Coolgardie, Esperance Plains, Jarrah Forest, Mallee, Swan Coastal Plain, Warren.
IBRA Subregions: Avon Wheatbelt P1, Avon Wheatbelt P2, Eastern Mallee, Fitzgerald, Northern Jarrah Forest, Perth, Recherche, Southern Cross, Southern Jarrah Forest, Warren, Western Mallee.
IMCRA Regions: Leeuwin-Naturaliste, WA South Coast.
Local Government Areas (LGAs): Albany, Augusta-Margaret River, Bayswater, Beverley, Boyup Brook, Bridgetown-Greenbushes, Chittering, Cockburn, Cranbrook, Denmark, Dundas, Esperance, Gingin, Gnowangerup, Harvey, Jerramungup, Kellerberrin, Kent, Kulin, Manjimup, Nannup, Narrogin, Perth, Plantagenet, Ravensthorpe, Rockingham, Serpentine-Jarrahdale, Stirling, Swan, Wagin, Wanneroo, Yilgarn, York.
Alternative Names. Common Thistle, Black Thistle, Bull thistle, Scotch Thistle.
General Biology. Growth form. Herb. Life form. Annual. Reproduction. Seed. Dispersal. Wind, water, machinery, animals (particularly birds consuming seed, collecting the silken tassels for nests). Seedbank persistence. Highly variable. Seed in the top 2cm of mostly disappears in one year but may last up to four years. Seed buried at 20cm may last up to 50 years. Fire response. Resprouts after fire. Fire creates conditions suitable for mass germination of soil-stored seed.
Notes. Occurs in subhumid to cool-temperate regions usually on more fertile heavier soils. An aggressive weed in disturbed sites. Can be biennial. Flowers are hermaphrodite (have both male and female parts), are self-pollinated or cross-pollinated by bees, flies, moths, butterflies and beetles. Intolerant of shade and requires moist soil to establish. Can be dispersed by the wind over a large area, however the pappus can readily detach from seed at maturity, leading the majority of seeds to fall within a short distance of the parent plant. Seedlings and young rosettes are susceptible to drought over summer. After germination a major root system develops rapidly, whilst a rosette is more slowly formed above ground. Peak flowering normally occurs in late spring to early summer. Soil disturbance promotes germination. Seeds mature and may disperse within 7 to 10 days of flowering. Seed viability is high. Germination is stimulated by mositure, disturbance and/or nutrients. The rapid disappearance of seed from the soil surface means that management practises that result in seed burial should be avoided..
Additional information. Origin. Western Asia, Europe, North Africa. History of use/introduction. Food.
Suggested method of management and control. Glyphosate at 0.5% provides effective control of seedling and adult plants, alternatively spot spray Lontrel® 6 ml/10 L (300 ml/ha) + wetting agent, from rosette stage to early flowering. Blanket wipers or wick applicators using 50% glyphosate can provide some selective control. Eliminating seed production is the most effective mechanical control technique. Mowing/slashing at bud or early bloom stage will cause plants to resprout. However, close mowing or cutting twice per season will usually prevent seed production. 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.
Legend: Y = Yes, regularly, O = Occasionally, U = Uncertain, referred by others but not confirmed.
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Western Australian Herbarium (1998–). FloraBase—the Western Australian Flora. Department of Biodiversity, Conservation and Attractions. https://florabase.dpaw.wa.gov.au/