Hymenoxys ambigens is a species of flowering plant in the daisy family known by the common name Pinaleño Mountains rubberweed. It is native to the states of Arizona and New Mexico in the southwestern United States.Biota of North America Program 2014 distribution mapSEINet, Southwestern Biodiversity, Arizona chapter description, photos, distribution map
Hymenoxys ambigens is a perennial herb up to 150 cm (5 feet) tall. Leaves have very narrow lobes resembling branching threads. One plant can produce an array of 25–400 small yellow flower heads, each head with 3-5 ray flowers and 6–15 disc flowers.Flora of North America, Hymenoxys ambigens (S. F. Blake) Bierner, 1994. Pinaleño Mountains rubberweed Blake, Sydney Fay 1929. Journal of the Washington Academy of Sciences 19(13): 276–278 description and commentary in English, full page of line drawings on page 277
Varieties Hymenoxys ambigens var. ambigens - Mescal, Pinaleño, and Santa Teresa Mountains in Arizona Hymenoxys ambigens var. floribunda (A.Gray) W.L.Wagner - Chiricahua, Dos Cabezas, Dragoon, Little Dragoon, and Mule Mountains in Arizona Hymenoxys ambigens var. neomexicana W. L. Wagner - Animas + Peloncillo Mountains in New Mexico
History In 1882, Sarah Plummer Lemmon discovered the species. Harvard University botanist, Asa Gray, first described the species, naming it Plummera floribunda in her honor. Plummera was redefined as a subgenus of Hymenoxys in 1994.Bierner, Mark W 1994 SUBMERSION OF DUGALDIA AND PLUMMERA IN HYMENOXYS (ASTERACEAE: HELIANTHEAE: GAILLARDIINAE) Sida, Contributions To Botany Volume: 16:1-8
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