Invasive Plant: Italian Thistle or Slender Flowered Thistle

Information
Photo shows a field of narrow plants with spikes and tiny, brush-like, light-pink flowers.
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.
On this page

At a Glance

  • Photo shows a close up of narrow plants with spikes and tiny, brush-like, light-pink flowers.
    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.

Resource

Contact

Early Detection and Rapid Response (Invasive Plants)

Environmental Services
mitch.bixby@portlandoregon.gov
phone number503-823-2989

Topics

Environment
Water, stormwater, and sewer

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