Thursday, June 30, 2016

Invasive Alert - Meadow Knapweed


Day 261: Recently, the Invasive Plant Council asked me to lead an introductory walk for new members, and after some discussion of potential locations, we settled on Eatonville's Bud Blancher Trail with the option of continuing into Pack Forest. Since I walk Bud Blancher quite frequently in the winter months as part of the Park's fitness challenge, I expected that the trainees would find very little (if anything) to report. I figured we'd practice by taking GPS readings on ivy, holly and Stinky Bob (Herb Robert). Since these species are so prevalent, we don't include them in our surveys unless there's a good possibility that they can be controlled easily by the land manager for the area, except to make a note in our reports that they are present.

Due to the distance from urban centers, I only had one trainee sign up for my walk: a young botanist/teacher from Puyallup. I arrived on site early, and while I was waiting for him to arrive, I noticed something purple growing at the top of the berm beside the trail. It was obviously not a thistle, so I climbed up for a better look. Aaaaggghhhh! Meadow Knapweed! There were several instances of it along a little side-trail on city property, so when Ian arrived, I announced that we could start the day off with a "positive," i.e., we'd found an infestation. As we walked down the first half-mile of the trail, we found several more occurrences, including one patch about 40' in diameter.

Meadow Knapweed (Centaurea debeauxii) is a hybrid of two other species of knapweed, Centaurea jacea x nigra (Brown Knapweed and Black Knapweed). There are eight species on the list of invasives in Washington. They are best controlled by using a combination of techniques to prevent their spread. Pulling is often not enough and must be followed by chemical treatment. However, if you see knapweeds on your property, pull them from the base and bag them to prevent the heads from going to seed.

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