Isocarpha oppositifolia, the Rio Grande pearlhead, is a New World species of plants in the family Asteraceae. It is widely distributed in eastern and southern Mexico, Central America, the West Indies (Cuba, Jamaica, Bahamas, Caymans, Trinidad), and northern South America (Colombia, Venezuela). The range extends northward, just barely crossing to the north side of the Río Grande in the two southernmost counties in Texas (Cameron + Hidalgo).Biota of North America Program 2014 county distribution mapDavid J. Keil & Tod F. Stuessy. 1981. Systematics of Isocarpha (Compositae: Eupatorieae). Systematic Botany (1981) 6(3): pp. 258-287 descriptions, line drawings, distribution maps for all 5 species
Isocarpha oppositifolia is an herb or subshrub up to tall. Leaves are up to long, usually narrow but sometimes egg-shaped. One plant produces several flower heads, each a long flower stalk, each head with 60-150 disc flowers but no ray flowers.
References
External links Conabio, ficha informativa, Isocarpha oppositifolia (L.) Cass. in Spanish with photos Photo of herbarium specimen at Missouri Botanical Garden, collected in Guatemala in 2008