Report #187 - Report: Diffuse Knapweed (Centaurea diffusa)

Diffuse Knapweed (Centaurea diffusa) on Jul 29, 2008

Originally reported as Russian Knapweed (Acroptilon repens)

Submitter does not have a specimen

Description of specimen

Okay, I think it's diffuse knapweed, but that's not a choice. I've pulled a lot of knapweed for TNC, so I *know* it's a knapweed. Definitely not meadow knapweed. Could be Russian or Squarrose...it was fairly whitish though. I didn't see any pinkish or purplish parts...

Commentary

There's loads of Canadian Thistle here, too.

Reporter
July 29, 2008, 8:07 a.m.

Hi April!

Thanks for your report of what could be Russian knapweed. This is a species we definitely don’t want to see in Portland. I will forward it to Lucas Nipp at East Multnomah SWCD and see if he would be willing to go check it out and confirm.

Thanks!

Tania Siemens
OSU Sea Grant/The Nature Conservancy
tania.siemens@oregonstate.edu

Thanks!

Tania Siemens
July 30, 2008, 4:48 a.m.

Location

Hi! I was riding the Portland Streetcar from a baby shower on Saturday afternoon that was in the John Ross Building in South Waterfront. The streetcar passes by tons of blackberry, Canada thistle, bull thistle, etc., but the most disturbing to me was the obvious large amounts of what looked to me like diffuse knapweed. Now, I'm positive it's a knapweed. It doesn't look like meadow, because that's beefier and purple. It has lots of little whitish flowers and it nicely runs along the streetcar line and I'm sure the streetcar is nicely distributing its seeds like crazy. I saw at least 20 big plants and that was from the streetcar without being able to hold still. It's right along SW Moody along side of where the streetcar runs.

Diffuse Knapweed (Centaurea diffusa) on Jul 29, 2008

Description of specimen

Commentary

Location

Expert Reviewer