Plants 20-120 cm (sometimes robust); self-incompatible (herbage glaucescent, acrid-scented). Stems (usually reddish) usually branched (branches 1-15+, remote, arcuate-ascending, slender, arising mostly distal to midpoints of main stems), glabrous or ± scabrous distally. Leaves mostly alternate, 2-10 cm (at least proximal), hispidulous to hispid and± long-hairy (at least margins and adaxial faces), sometimes with tack-glands. Heads in spiciform arrays (usually l-3 per node). Peduncular bracts ± narrowly elliptic, 1-12 mm (± glabrous or hispidulous to hispid, sometimes ± bristly and/or pectinate-fimbriate), apices ± truncate, tack-glands (0-) 1 (terminal). Phyllaries 5-10 mm, abaxial faces glabrous or sparsely strigose and/or long-straight-hairy, especially distally, shaggy-long hairy on distal margins, tack-glands usually 0. Paleae 5-10 mm (tack-glands 0). Ray florets 3-6; corollas yellow, tubes ca. 2.5 mm, ± papillate, throats sometimes with red 'eyes,' laminae (4-)5-12 mm (central lobes smaller than laterals, symmetric, widest at bases, laterals asymmetric, sinuses less than ¹/3 laminae). Disc florets 3-25 (ovaries often sterile or of low fertility); corollas yellow, 4-6 mm (sometimes papillate distally, lobes± hirsute; anthers yellow, light brown, or dark purple). Ray cypselae ca. 3 mm, rough-wrinkled, glabrous. Disc cypselae 2-4 mm, glabrous or ± appressed-hairy; pappi 0 or of 7-12 oblong, fimbriate scales, to 1 mm. 2n = 14.

Flowering spring-fall. Dry, open hillsides, rocky ridges, talus; 50-1500 m; Calif., Oreg.

Calycadenia truncata is the most widespread of all of the taxa. It ranges from Jackson and Josephine counties in southwestern Oregon [reported by D. D. Keck (1960b) from Douglas County] in the Coast Range to San Luis Obispo County, California, and in the Sierra Nevada foothills south to Fresno County. It is also localized in sites in the Sacramento Valley.