Purple Starthistle

Centaurea calcitrapa

Purple Starthistle

Family: Asteraceae

Weed class: A
Year Listed: 1989
Native to: Asia Minor from a region between the Black and Caspian seas
Is this Weed Toxic?:

not known to be

Legal listings:

WAC 16-752; WSDA Quarantine list (prohibited plant list)

Why Is It a Noxious Weed?

Similar to yellow starthistle, this is an aggressive Centaurea, which is a major problem on annual rangelands in the San Francisco Bay area.

How would I identify it?

General Description

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.

Flower Description

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).

Leaf description

Lower leaves deeply divided, upper leaves are narrow and undivided.

Stem description

Purple starthistle stems are branched and angled, not winged.

Fruit Seed Description

Purple starthistle seed is small (0.10 to 0.13 inches), white or brown streaked in color and hairless.

Where does it grow?

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.

How Does it Reproduce?

Purple starthistle reproduces by seed.

How Do I Control It?

Mechanical Control

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.

Herbicide Control

Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.

For More Information

See our postcard for early detection information about purple starthistle.

See our Written Findings for more information about purple starthistle (Centaurea calcitrapa).

Report on purple starthistle from the book "Weed Control in Natural Areas in the Western United States"

Additional Photos