129c. Eriogonum arcuatum Greene var. xanthum (Small) Reveal, Harvard Pap. Bot. 9: 157. 2004.
Ivy League wild buckwheat
Eriogonum xanthum Small, Bull. Torrey Bot. Club. 33: 51. 1906; E. chloranthum Greene; E. flavum Nuttall subsp. chloranthum (Greene) S. Stokes; E. flavum var. xanthum (Small) S. Stokes; E. jamesii Bentham var. xanthum (Small) Reveal
Plants compact mats, 3-10 dm wide. Aerial flowering stems 0.2-0.8 dm. Leaf blades oblanceolate to oblong, 1-2.5 × 0.5-1 cm. Inflorescences capitate, often reduced to single involucre; bracts 0.3-1 × 0.2-0.7 cm. Involucres 4-6 × 3-5 mm. Flowers 6-7 mm.
Flowering Jul-Sep. Sandy, gravelly to rocky or talus slopes, high-elevation grassland, sagebrush, and tundra communities, alpine conifer woodlands; (2600-)3000-4000(-4200) m; Colo.
Variety xanthum is the subalpine to alpine expression of the species and is distributed along the backbone of the Colorado Rocky Mountains on many of the highest peaks (Chaffee, Clear Creek, Custer, El Paso, Fremont, Grand, Hinsdale, Huerfano, Lake, Larimer, Park, Saguache, Summit, and Teller counties). The plants are rather exquisite in the field and do well in cultivation.