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This monoecious weedy species is a late spring emergent that sets seeds in late summer and early fall. It is a species of disturbed ground. Hybrids between this species and the common ragweed Ambrosia artemisiifolia) have been observed. The two species can be separated by leaf morphology. Plants can go unnoticed because of their overall green colour and lack of showy flowers.
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General: Perennial from creeping rhizomes; stems slender, stiff-hairy, branched, at least above, 30-100 cm tall.
Leaves: Alternate above, opposite below, triangular to rounded in outline, 4-10 cm long, nearly unstalked or short-stalked, usually only once-pinnately cut, often toothed, stiff-hairy, uppermost leaves narrower and less divided.
Flowers: Male (sterile) heads numerous in terminal, elongate, often panicled racemes; female (fruiting) heads solitary or clustered in upper leaf axils; fruiting involucres short-beaked, 3 mm long, stiff-hairy and glandular, bearing 1-6, abruptly sharp-pointed, short, conic tubercles at the apex.
Fruits: Achenes egg-shaped, about 3 mm long, hairy, glandular, with short, conic tubercles around apex of body; pappus lacking.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2020. E-Flora BC:
Electronic Atlas of the Plants of British Columbia [eflora.bc.ca]. Lab for
Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2021-07-25 6:55:55 AM
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