Horseweed/marestail Conyza Canadensis (L.) Cronq.
Family: Asteraceae (Composite family)
Life cycle: Winter (primarily) and summer annual
Native status: Native to North America
Habitat: Disturbed areas, no-till fields
General description: Produces a basal rosette of hairy, irregularly toothed leaves 2-3 inches long. Stem reaches heights of 6 ft, terminal portion is a large panicle of inconspicuous flowers producing numerous wind-dispersed seed. Pubescent stem covered with alternately arranged, hairy leaves 3- 4 inches long
Key ID traits: Hairy, lanceolate or linear leaves. Lower leaves irregularly toothed.
Miscellaneous: Horseweed is commonly called marestail in Iowa. In typical years, about ¾ of the population germinates in late summer/fall, the remainder the following spring. It was the first weed to develop resistance to glyphosate in glyphosate resistant crops. Resistance spread rapidly due to wind-dispersed seed.