In the heat of summer in the Rogue Valley, yellow starthistle (Centaurea solstitialis) raises heads of brilliant yellow flowers rigidly defended by sharp spines. Although bees reap double benefits of nectar and pollen during a season when most native plants no longer are flowering, this nonnative weed is a threat...
Squarrose knapweed, introduced from southwest Asia and the Middle East, became weedy in northern California and Utah by the early 1950s. How it
was originally introduced is not known, but its spread in California
and Utah was associated with the trailing of range sheep. Squarrose knapweed grows in the Klamath,...