Spotted Knapweed (Yukon Invasive Species )

Spotted Knapweed

Centaurea stoebe

Summary ²

Knapweeds resemble thistles but lack spiny leaves and stems. They are biennial or short-lived perennials. This
species reproduces entirely by seed. Large plants can produce over 20,000 seeds. It has not been known to be a problem in Yukon, but to date it has not had a chance to get established here. British Columbia and Alaska have active programs of eradication. Spotted Knapweed is a restricted noxious weed in BC.

Range in Yukon ³

Spotted Knapweed has been reported from the Alaska Highway near Hays Creek, the Carcross Desert. One site just north of Haines Junction along the Alaska Highway.

Similar Species ³

Corn Flower (Centaurea cyanus) is an annual garden plant that is sometimes found in commercial “wild flower” mixes. It is occasionally found on roadsides but is not known to persist.

Ecological Impact ³

Knapweeds may invade undisturbed grasslands and produce chemicals that hinder growth and germination of other plants, reducing biodiversity and changing community structure. Also, grazing animals dislike the bitter taste of knapweed so it reduces the productivity of forage lands.

Control ³

The seeds of thistle and knapweed continue to mature after pulling. You may put plants into clear garbage bags and then leave them in the sun to kill off the plants and roast the seeds.

Sources and Credits

(c) Matt Lavin, some rights reserved (CC BY-SA), http://www.flickr.com/photos/35478170@N08/3768272782
Adapted by stephw782 from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Centaurea_stoebe
(c) stephw782, some rights reserved (CC BY-SA)

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