Did you manage to guess this week’s “I Spy” invasive? High-five if you did, and high-five if you tried, because it was a tricky one that not many people can guess correctly!
Diffuse Knapweed (Centaurea diffusa) is a biennial or short-lived perennial that was brought to North America as a hay contaminant in crop seeds from the Eastern Mediterranean.
Diffuse Knapweed can grow 0.1 – 0.6 m tall and has a single, erect stem with multiple branches. Stems and branches are covered with stiff, white hairs. The flowers are small, white (sometimes rose-purple or lavender) and form in either small clusters, or alone on the end of branches. The leaves are stalkless and become bract-like near the flowers. The rosettes and lower leaves are 5 – 20 cm long, rough, hairy and divided.
Diffuse Knapweed can be found growing in disturbed, dry areas such as sandy areas, grasslands, pastures, woodland clearings, open forests, roadsides, right-of-ways and clear-cuts.
Be aware, there is a Diffuse Knapweed look-alike that’s also invasive and can be found in the Sea to Sky Region. Spotted Knapweed (Centaurea bierberstienii) has hairy, deeply-cut leaves with the lower leaves having a black-tipped fringe, which gives it its spotted appearance. Flowers are purple, and on occasion, white, growing on a single or multiple upright stems that can be 1 m tall.