- Cardaria draba
Hoary cress (Cardaria draba) is a perennial plant that invades hay fields, rangeland meadows and along roadsides, competing with native vegetation. It can be found on open, unshaded areas at low- to mid-elevations on the coast, and interior grassland and forest regions of BC. It spreads primarily by roots and seed dispersal; each plant can produce up to 4800 seeds. Plants grows to 0.6 m high. One plant can spread up to 3.5m2 in one year with no competition nearby.
Considered regionally noxious under the BC Weed Control Act, hoary cress was most likely brought to North America in contaminated alfalfa seeds during the 1800s, and can still spread the same way. Also known as “white-top,” hoary cress has white flowers with four petals, giving it a flat-topped appearance. Arrowhead-shaped leaves adorn the stem and are covered with soft white hairs, giving the foliage a grey-green appearance.
Hoary cress is a concern in the agricultural regions of the Okanagan and Thompson, and present in the Kootenays and Cariboo, but less frequent in southern BC.