Hoary Cress (Cardaria draba (L.) Desv.)
Perennial forb in the Mustard Family. Grows up to 50cm tall with numerous white flowers with 4 petals giving it a flat-topped appearance. Leaves are alternate, 4-10cm long, blue-green colour up the stem. Rhizomatous roots at a depth of 75-80cm but recorded up to 9m deep. Heart-shaped seed capsules hold 2 reddish-brown seeds.
Habitat and Ecology
Low to mid-elevations in BC’s grasslands and forests, dry roadsides, fields and disturbed habitats. Grows well on alkaline soils, pastures, meadows, croplands, open and un-shaded disturbed ground.
Highly competitive weed spreads mainly by roots and can out compete native vegetation on rangelands. One plant can spread up to 3.5m2 in one year with no competition nearby.
Mowing several times in a season can decrease seed production. Sheep grazing may manage it as well. Cultivation will manage it successfully if tillage begins at the flower bud stage and is repeated every 10 days in the growing season. Multiple herbicide applications are needed to provide control. Consult the most recent BC Ministry of Agriculture, Food &Fisheries, Crop Production Guides for specific recommendations.
Province of British Columbia. 2002. Guide to Weeds in British Columbia.