Italian thistle or slender flowered thistle is on the Required Eradication List. All sightings should be reported. Learn more about how to report this plant.
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At a Glance
- Scientific name: Carduus pycnocephalus, Carduus tenuiflorus
- Blooms May to June.
- Flowers are purplish to pinkish in cylindrical heads, either solitary or in clusters.
- Grows 1 to 4 feet tall.
- Stems have spiny wings.
- Leaves deeply cut into 2 to 5 pairs of lobes, have white spots and undersurface slightly woolly.
- Oregon Department of Agriculture noxious weed rank: B
- Report patches of this plant? Yes. City code lists this as a Required Eradication species. Report all sightings to Portland’s Environmental Services (contact information on this page). Management of this plant is required, but free help is available.
- Oregon Department of Agriculture PDF weed profile for Italian thistle.