Invasive Plant Guide: Giant PlumelessThistle
- Flower color: pink-purple
- Flowers:July to September
- Stems: partly winged; spiny. Multiple flower-heads at end of stems.
- Plant height: ranges from about 1 foot to 6 feet
- Leaves: very spiny
Growth habit: annual/biennial
Open disturbed sites, roadsides, fields, pastures, hillsides, rangeland, forest openings. Prefers warm, dry climate areas. Tolerates a wide range of soil types.
Giant plumeless thistle (Carduus acanthoides) is found in only one location in the mid-Klamath. This is also the only known location in all of Siskiyou County.
Plant spreads by seed only. Seeds are viable for up to seven years, and germinate aggressively.
- California Invasive Plants Council
- California Department of Food & Agriculture