RAGWEED IN SOUTHEASTERN ALBERTA

Abstract

Recent surveys show that common ragweed, Ambrosia artemisiifolia var. elatior, is prevalent in two regions of southeastern Alberta and adjacent Saskatchewan, (a) an area with Medicine Hat as approximate center, (b) a narrow area east and west of Empress. The weed appears to be firmly established in depressions and on slough borders of natural prairie and of cultivated land. Available evidence points to the conclusion that the species was introduced to the Canadian plains, though the possibility that it was indigenous there cannot be dismissed. The question of its probable spread westward and northward is discussed.