The biology of Canadian weeds. 138. Kochia scoparia (L.) Schrad.

Kochia [Kochia scoparia (L.) Schrad.] is an annual broadleaf weed species native to Eurasia and introduced as an ornamental to the Americas by immigrants in the mid- to late 1800s. Although sometimes categorized in the genus Bassia, there is no compelling reason for this classification. This naturalized species is a common and economically important weed in crop production systems and ruderal areas in semiarid to arid regions of North America, and has expanded northward in the Canadian Prairies during the past 30 yr. Although primarily self-pollinated, substantial pollen-mediated gene flow and efficient seed dispersal aids both short- and long-distance spread. The weed is morphologically highly variable, and its growth and development are markedly affected by environmental conditions. Kochia, a C4 species, is highly competitive in cropping systems because of its ability to germinate at low soil temperatures and emerge early, grow rapidly, tolerate heat, drought and salinity, and exert allelopathic effects...