Plant
Cotton Thistle
Onopordum acanthiumAlso known as Scotch Thistle, Heraldic Thistle, Woolly Thistle
Cotton thistle dominates disturbed soils and rangelands with its towering stature, silvery-white woolly foliage, and fiercely spined wings running down the stems. During its first year, it forms a sprawling rosette up to a meter across before bolting in its second summer to produce heavy globose heads of vibrant purple florets. Its dense growth and prolific seed production allow it to displace native vegetation, creating impenetrable, prickly thickets that deter livestock and wildlife.
BiennialSpinyInvasive
—observations
—countries
—peak records
Least ConcernConservation statusIUCN Red List categoriesLCNTVUENCREWEXLeast ConcernRed List categories, explained →
Diet & preyAutotrophic (photosynthetic)
Predators
- Larinus latus (seed weevil)
- Trichosirocalus briesei (crown weevil)
- Painted Lady Caterpillar
ThreatsHerbicide application, biocontrol weevils, and mechanical mowing
HabitatsPastures, roadsides, waste ground, dry grasslands, and riverbanks
Life span2 years (biennial)
Classification
- OrderAsterales
- FamilyAsteraceae
- GenusOnopordum
- SpeciesOnopordum acanthium
Range data is not available yet.
Interaction riskLow
- Low
- Moderate
- High
- Very high
- Why interaction risk is low
- Safe to observe, but stems and foliage bear sharp spines that can pierce bare skin.
Responsible observation
- Wear heavy gloves: Handle thick gloves and sturdy clothing to avoid puncture wounds from stiff spines.
- Prevent seed dispersal: Avoid brushing seed heads onto clothing or vehicles to avoid spreading this weed.
Competitor (c) Sandy Wolkenberg, some rights reserved (CC BY), uploaded by Sandy Wolkenberg · cc-by
Competitor (c) Michael J. Papay, some rights reserved (CC BY), uploaded by Michael J. Papay · cc-by
Pollinator Andreas Trepte / CC BY-SA 2.5 · cc-by-sa
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