Yellowstone sulphur flower

Eriogonum rydbergii Greene

Herbs, compact mats, 1-2 × 2-5 dm. Aerial flowering stems erect, 1-2 dm, tomentose to densely floccose, without one or more leaflike bracts ca. midlength. Leaves in tight rosettes; blade usually elliptic to ovate, 1-2 × 0.5-1.5 cm, lanate to densely tomentose on both surfaces, margins plane. Inflorescences umbellate; branches 0.3-2.5 cm, without a whorl of bracts about midlength; involucral tubes 2-3 mm, lobes 1.5-3 mm. Flowers 4-7 mm; perianth bright yellow.

Flowering Jun-Sep. Sandy to gravelly flats, sagebrush communities, montane conifer woodlands; 2000-2300 m; Wyo.

Variety cladophorum is a rare and localized expression known from three locations (Upper Geyser Basin, Old Faithful, and Madison Junction) within Yellowstone National Park, Teton County.