13. Pyrrocoma radiata Nuttall, Trans. Amer. Philos. Soc., n. s. 7: 333. 1840.
Snake River goldenweed
Haplopappus carthamoides (Hooker) A. Gray var. maximus A. Gray; H. radiatus (Nuttall) Cronquist
Plants 40–90 cm. Stems 1–8, usually erect, rarely curved-ascending, pale, rarely reddish, robust, glabrous, eglandular. Leaves: basal (tufted), long-petiolate, blades (pale) broadly elliptic to obovate, 100–500 × 40–200 mm, rigid, margins entire or undulate, occasionally spinulose-serrate, eciliate; cauline reduced and becoming sessile distally, margins entire or sharply spinulose-serrate; faces glabrous. Heads borne singly or 3–12 in short, open corymbiform arrays (subtended by leaflike bracts). Peduncles 2–7 cm. Involucres broadly hemispheric, 20–32 × 25–40 mm. Phyllaries in 5–6 series, loosely appressed, ovate-oblong, unequal, margins pale, entire, eciliate, apices green, tip reflexed, faces glabrous. Ray florets 17–34; corollas inconspicuous, 7–13 mm. Disc florets 80–100; corollas 10–15 mm. Cypselae subcylindric, 6–11 mm, 4-angled, faces glabrous; pappi tawny or brownish, 9–13 mm. 2n = 36.
Flowering Jun–Sep. Dry hillsides, alkaline slopes; 600–2400 m; Idaho, Oreg.
Pyrrocoma radiata is known only from the southern end of the Snake River canyon in Oregon and Idaho. It is considered endangered in Oregon. It is recognized by its large stature, glabrous herbage, and very large heads. It is most closely related to P. carthamoides and was formerly treated as a variety of that species. It is hexaploid and may be a gigas form of P. carthamoides.