While Scotch Broom may be the most apparent weed threat to the prairies of South Puget
Sound, it is far from the only meance. Several non-native forbs and grasses have invaded
the prairies, or threaten to do so, in numbers large enough to constitute an ecological
threat. This paper looks at five common weeds well established in the prairies of South
Puget Sound and at four weeds common elsewhere, but presently limited in distribution
in the Puget prairies. Consideration is given to growth habits, tolerances, propagative
methods, pests, and other characteristics which both makes these weeds plats of concern
and which potentially limits their spread. The paper first discusses two common invasive
grasses, colonial bentgrass (Agrostis tenuis), and velvet-grass (Holcus lanatus), and three
common invasive forbs, St. Johnswort (Hypericum perforatum), hairy cat’s ear
(Hypochaeris radicata), and ox-eye daisy (Chrysanthemum leucanthemum). This is
followed with discussion of four threatening wees, (gorse (Ulex europaeus), leafy spurge
(Euphorbia esula), spotted knapweed (Centurea maculosa), and mouse-eared hawkweed
(Hieracium pilosella), and some near relatives. The paper also looks at government
noxious weed programs and how their work can affect prairie conservation, and
concludes with a brief look at some issues prairie managers may face.
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