Aquatic Plants - invasive

Water Primrose (unknown species) (Ludwigia spp.) on Mar 14, 2011

Submitter does not have a specimen

Description of specimen

See attached picture

Commentary

Thanks for reporting this, Rick. It looks like one of the introduced water primroses (Ludwigia spp.), but difficult to say when it's still semi-dormant. Introduced water primroses are newly listed Class B Noxious weeds and are fairly widely spread through the Willamette Valley, from Eugene north to Portland.

I have a few other sites to visit down that way, so I'll drive down in the next month or so to have a look in person and will let you know what I find out. Can you direct me to where at the lake you take those photos?

Assuming it is Ludwigia, the extent of the plant around Waverly Lake might determine if control is warranted. We're working with a few groups here in Portland on control techniques - none are cheap when it's a sizable infestation.

Feel free to contact me if you have questions. I'll be in touch once I've had a chance to visit the site.

Vanessa Howard Morgan
Center for Lakes and Reservoirs, Portland State University
vhoward@pdx.edu
503-725-2937

Vanessa Howard Morgan
March 15, 2011, 1:16 p.m.

Rick, I got out to this site in April and there is indeed a good population of water primrose (most likely Ludwigia hexapetala) ringing Waverley Lake, along with some stands of yellow flag iris. In a setting like this, it looks as though manual removal might be fairly feasible from the shoreline, depending on how large and problematic this population gets. Not a minor undertaking, but worth it if recreational uses are being compromised.

If you have questions or need any assistance, please feel free to contact me.

Vanessa Howard Morgan
Center for Lakes and Reservoirs, Portland State University
vhoward@pdx.edu
503-725-2937

Vanessa Howard Morgan
June 7, 2011, 11:33 a.m.