Grand Valley desert trumpet

Eriogonum inflatum Torrey & Frémont var. fusiforme (Small) Reveal

Herbs, spreading, annual, (0.3-) 0.5-4 dm, essentially glabrous, green or occasionally yellow-green. Stems: caudex absent; aerial flowering stems erect, usually hollow and fistulose, 0.5-1.5 dm, glabrous, villous proximally. Leaves basal; petiole 1-3 cm, hirsute; blade round, 0.5-3 × 0.5-2.5 cm, short-hirsute and greenish on both surfaces, margins plane. Inflorescences cymose, open, spreading, 5-30 × 5-30 cm; branches fistulose, glabrous; bracts 3, scalelike, 1-2 × 1-1.5 mm. Peduncles erect, straight, filiform to capillary, 1-2 cm, glabrous. Involucres turbinate, 1-1.2 × 0.7-1 mm, glabrous; teeth (4-)5, erect, 0.4-0.6 mm. Flowers 1.3-1.6 mm; perianth yellow with greenish to reddish midribs, densely hirsute with coarse curved hairs; tepals monomorphic, ovate; stamens exserted, 1.3-1.8 mm; filaments sparsely pubescent proximally. Achenes light brown, lenticular to 3-gonous, 1.3-1.8(-2) mm, glabrous.

Flowering Apr-Jul. Heavy clay, sometimes gravelly flats and slopes, saltbush and greasewood communities, pinyon and/or juniper woodlands; (900-)1100-2000 m; Colo., Utah, Wyo.

Eriogonum fusiforme is widespread and common in southwestern Wyoming (Sweetwater County), eastern Utah (Carbon, Duchesne, Emery, Garfield, Grand, Kane, San Juan, Uintah, and Wayne counties), and adjacent western Colorado (Delta, Garfield, Mesa, Montrose, and Rio Blanco counties). In a “good” year, millions of individuals carpet the heavy clay flats and slopes (typically Mancos Shale), especially in Utah and Colorado. The plants can be so abundant and closely arranged that it can be difficult to walk through the tangle of stems and branches. This species is absolutely distinct from E. inflatum and no intermediates have ever been observed.