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FNA | Family List | FNA Vol. 5 | Polygonaceae | Eriogonum

107mm. Eriogonum umbellatum Torrey var. cognatum (Greene) Reveal, Southw. Naturalist. 13: 357. 1968.

Flagstaff sulphur flower

Eriogonum cognatum Greene, Pittonia 3: 201. 1897; E. umbellatum subsp. cognatum (Greene) S. Stokes

Herbs, compact mats, 1-2(-2.5) × 1-3 dm. Aerial flowering stems erect, 1-1.5 dm, glabrous, without one or more leaflike bracts ca. midlength. Leaves in loose rosettes; blade oblong-obovate to elliptic or oval, (1-)1.5-2(-2.5) × 1-1.5(-2) cm, densely white-tomentose abaxially, thinly floccose or glabrous and dark green adaxially, margins plane. Inflorescences compound-umbellate, branched 2-4 times; branches glabrous, without a whorl of bracts ca. midlength; involucral tubes 3-5 mm, lobes 1-2.5 mm. Flowers 4-7 mm; perianth bright yellow.

Flowering Jul-Sep. Sandy flats and slopes, sagebrush communities, oak and montane conifer woodlands; 1600-2200 m; Ariz.

Variety cognatum is localized and rather infrequent in south-central Coconino County and also barely enters Gila and Yavapai counties. It is seen most frequently in the greater Flagstaff area.


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