Land Plants - invasive

Meadow Knapweed (Centaurea × moncktonii) on Sep 4, 2009

Submitter has sample
EDRR Status: Local expert notified

Description of specimen

Tall, thin stems with narrow leaves, and branching near top with thistle-like flowers, purple, with shape like Bachelor's Button (another Centaura). There was quite a bit of it along the guard rail. Earlier I had reported some around the electric station just a bit east of there, and they have done a thorough job of mowing that, so I don't know if that will take care of it for long, but at least they are making some effort.


Dear Karen,

Thanks for your report! It sounds like this could be Canada thistle, a very abundant weed in that area. Or, it may be meadow knapweed, which is also very abundant. I will pass this along to ODOT, but I think they are aware of the situation. If you have a photos, or could look up these species on the internet to confirm what you saw, that would help me determine how to respond.

Please keep up the good work reporting invasive species. I am sorry for the delay in response. summer is a busy time, but we really do value volunteers like you keeping an eye out for new invasive species. In that area species like shining geranium, herb Robert, and spurge laurel are also priority.

Thanks again and keep up the good work.


Tania Siemens
Invasive Species Early Detection and Rapid Response Coordinator
The Nature Conservancy
WISE Program Coordinator (Watershed and Invasive Species Education)
Oregon Sea Grant Extension

Tania Siemens
Oct. 22, 2009, 7:03 a.m.