107c. Eriogonum umbellatum Torrey var. stragulum Reveal, Phytologia. 86: 156. 2004.
Spreading sulphur flower
Herbs, spreading mats, 1-3.5(-4) × 2.5-10(-12) dm. Aerial flowering stems erect, 1-3 dm, thinly floccose, without one or more leaflike bracts ca. midlength. Leaves in loose rosettes; blade broadly elliptic to ovate, (0.8-)2-3(-3.5) × (0.7-)1-2(-2.5) cm, thinly tomentose to sparsely floccose abaxially, thinly floccose or glabrous and green adaxially, margins plane. Inflorescences umbellate; branches (1-)2.5-5(-8) cm, without a whorl of bracts ca. midlength; involucral tubes 2-3 mm, lobes 3-5 mm. Flowers 4-7(-8) mm; perianth bright yellow. 2n = 80.
Flowering May-Sep. Sandy to gravelly or occasionally rocky flats and slopes, mixed grassland and sagebrush communities, juniper and montane conifer woodlands; 1400-2500 m; Idaho, Nev., Wyo.
Variety stragulum is the common expression of the species across southern Idaho (Bannock, Boise, Camas, Custer, Elmore, Gooding, Twin Falls, and Valley counties), mainly in the foothills and mountains adjacent to the Snake River Plains. It occurs also just to the east in Teton County, Wyoming. A collection from extreme northeastern Elko County, Nevada (Morefield & Price 5566, NESH, NY, RENO) with much shorter leaves and inflorescence branches is tentatively included. The variety forms large, spreading mats with largish leaves in rather loose rosettes. It is often found growing intermixed with E. heracleoides. Spreading sulphur flower is worthy of cultivation.