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Xanthisma coloradoense

Xanthisma coloradoense

Xanthisma coloradoense

Xanthisma coloradoense

Xanthisma coloradoense
Xanthisma coloradoense. Synonyms: Machaeranthera coloradoensis, Aster coloradoensis. (Colorado Tansy Aster).
Asteraceae (Sunflower Family)

Subalpine, alpine.  Meadows, openings, rocks, tundra. Summer.
Colorado Trail near Stony Pass, July 22, 2012.

Xanthisma coloradoense occurs in small populations in a few counties of two states:  Colorado (western counties) and Wyoming (south-central counties).  The plant's existence is threatened (it is a United States Forest Service Rocky Mountain Region Sensitive Species); if you see it or would like more information about it, contact the USFS at (970) 882-7296.

Xanthisma coloradoense is a low, mat-forming perennial herb with a woody base and taproot.  Its leaves are 1-4 cm long, spatulate to linear shaped, coarsely-toothed, and densely hairy.  Stems are covered with a gray-white pubescence and grow 4-10 cm high.  Inflorescences are large and solitary on short stalks.  Ray flowers range in color from pink to rose to purple and are 8-10mm long.  Phyllaries are sharp-tipped in 2-3 overlapping rows.

Xanthisma coloradoense
Xanthisma coloradoense. Synonyms: Machaeranthera coloradoensis, Aster coloradoensis. (Colorado Tansy Aster).
Asteraceae (Sunflower Family)

Subalpine, alpine.  Meadows, openings, rocks, tundra. Summer.
Colorado Trail near Stony Pass, July 22, 2012.

This plant was first found for science by Townshend Brandegee (in 1874 with the Hayden Expedition) at about 12,000 feet on the San Juan Pass in the San Juan Mountains of Southwestern Colorado.  Asa Gray named this specimen Aster coloradoensis and Brandegee notes that the plant is "found in the mountains of Northern Colorado by nearly all collectors, and passed over as a form of a species of Machaeranthera".  A number of renamings followed Gray's classification, and in 1927 George Osterhout placed the species in the Machaeranthera genus.  In 2004 research published by Morgan and Hartman proposed renaming the plant Xanthisma coloradoense.

Past classification of this plant also indicated that the species that Brandegee collected should be called Xanthisma coloradoense subspecies brandegeei to distinguish it from Xanthisma coloradoense subspecies coloradoensis.  Recent Forest Service research indicates that distinguishing between the two subspecies "was found to be difficult" and that the new classification into the Xanthisma genus will not recognize any subspecies.

 

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for  Xanthisma coloradoense