Land Plants - invasive

Giant Hogweed (Heracleum mantegazzianum) on May 1, 2008

Submitter does not have a specimen

Description of specimen

Giant Hogweed in several patches along the Fanno Creek. The plants vary from a foot tall now to several feet tall. Some are just one plant and other patches contain many plants.

Commentary

The Fanno Creek drainage is a historic giant hogweed site. The Oregon Department of Agriculture has been doing treatment of hogweed on this site for several years and we are getting significant decreases in density due to these treatments.

Treatments have not started yet for 2008 but this all hogweed on this site will be treated by ODA staff during the next month or so.

Thank you for your submission,

Tim Butler, ODA Noxious Weed Control Program

Tim Butler
May 8, 2008, 9:15 a.m.

Resources

There are many plants that look similar to giant hogweed, including our native cow parsnip. Giant hogweed is truly giant, often 7' to 14' tall, with leaves that can be up to 5' wide. There are some great photos comparing giant hogweed to similar species on the New York Dept of Environmental Conservation website.

Location

There are several patches of Giant Hogweed along Fanno Creek south of the Tigard libary. The first patch is behind the condominiums just south of the Library. There are several plants along the path heading south and a huge patch (difficult to reach and photograph because of blackberries) near a man-made erosion control structure below a big bend in the creek where it enters an area with single-family homes. There is a small patch on the other side of the creek too (at least one). I wouldn't be surprised if there was more Hogweed further downstream too but I haven't explored further yet. NOTE: I reported this Hogweed before but it was not big enough to identify for sure. I think it is now. I've attached new pictures.

Expert Reviewer

Mr. Tim Butler

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