Purple Starthistle
Centaurea calcitrapa
Washington State Classification
Class A — Eradication Required Statewide
Similar to yellow starthistle, this is an aggressive Centaurea, which is a major problem on annual rangelands in the San Francisco Bay area.
Quick Reference
Identification
Growth Habit
Upright branched annual, biennial or short-lived perennial plant growing up to 3.3 feet tall. It is covered with cobwebby hairs often becoming smooth with maturity.
Leaves
Lower leaves deeply divided, upper leaves are narrow and undivided.
Flowers
Narrow flowerheads of lavender to deep purple flowers. Spine-tipped bracts subtend the flowerhead with some spines longer at 0.4 to 1.2 inches (1cm to 3cm).
Fruit & Seeds
Purple starthistle seed is small (0.10 to 0.13 inches), white or brown streaked in color and hairless.
Impact
Similar to yellow starthistle, this is an aggressive Centaurea, which is a major problem on annual rangelands in the San Francisco Bay area.
Ecology & Spread
Habitat
It can grow in fields, roadsides, disturbed areas, grasslands and overgrazed rangelands. Please click here to see a county level distribution map of purple starthistle in Washington.
Spread Mechanisms
Reproduction
Purple starthistle reproduces by seed.
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Control Methods
Mechanical
- Grubbing or digging can be effective for small infestations. Mowing is not effective.
Biological Control
- No biological control program is currently being developed for purple starthistle.