Parthenium
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Authority
Acevedo-Rodríguez, Pedro & collaborators. 1996. Flora of St. John, U.S. Virgin Islands. Mem. New York Bot. Gard. 78: 1-581.
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Family
Asteraceae
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Scientific Name
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Description
Genus Description - Annual or perennial erect herbs or shrubs; stems usually much branched, tomentose or scabrous. Leaves alternate, simple, and entire to dentate or pinnately dissected. Inflorescence solitary in terminal corymbs or panicles. Heads small, radiate; involucre biseriate or few-seriate, broad, appressed, dry, subequal or the outer ones gradually shorter; receptacle small, convex, paleate, the palea membranous, subtending the outer disk flowers. Ray flowers 5, pistillate; corollas usually white, ca. 1 mm long. Disk flowers many, all except those of the outer row sterile and falling as a unit, at least some flowers of outer row functionally male and attached to the ray flowers; anthers white or yellow. Achenes dorsally compressed, those of the rays fertile and each ray achene forming a unit by fusing with the subtending involucral bract and 2 outer disk flowers and their palea; pappus of 2 or 3 short or elongate awns or lacking.
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Distribution
A genus of 16 or more species, all but 1 species restricted to North America and Mexico.
Saint John Virgin Islands of the United States South America| North America| México Mexico North America|