191. Oreostemma Greene, Pittonia. 4: 224. 1900.
Mountaincrown [Greek oreo, mountain, and stemma, crown]
Guy L. Nesom
Oreastrum Greene, Pittonia 3: 146. 1896, not Oriastrum Poeppig 1843
Perennials, 2–40(–70) cm (taproots, sometimes thickly rhizomatous, sometimes with branching caudices). Stems decumbent-ascending to erect, simple (essentially scapose), usually distally finely, loosely tomentose, sometimes stipitate-glandular. Leaves mostly basal (persistent rosettes), cauline reduced; alternate; sessile; blades 3-nerved, linear to oblanceolate, margins entire (apices acute to obtuse or rounded ), faces glabrous, sparsely villous, or stipitate-glandular. Heads radiate, borne singly. Involucres broadly turbinate, (5–12 ×) 10–20 mm. Phyllaries 25–40 in (2–)3–4 series, appressed (commonly purplish), 1(–3)-nerved (thin, not resinous; often low-keeled), linear to linear-elliptic or oblanceolate, subequal, usually herbaceous, sometimes proximal margins indurate, faces finely and loosely tomentose. Receptacles flat, shallowly pitted, epaleate. Ray florets 10–40, pistillate, fertile; corollas white, often drying blue to purple. Disc florets 30–55, bisexual, fertile; corollas yellowish at maturity, tubes shorter than tubular throats (barely constricted), lobes 5, erect, lanceolate to deltate; style-branch appendages linear-lanceolate. Cypselae (brownish) narrowly cylindric, ribs 5–10 (raised), faces glabrous or sparsely strigillose; pappi persistent, of 25–40, tawny-white, barbellate, apically attenuate bristles in 1 series, sometimes plus shorter bristles or setae in a second, outer series. x = 9.
Species 3 (3 in the flora): w United States.
Oreostemma is distinguished by its basal rosettes of narrow, 3-nerved leaves, single heads on scapose stems, turbinate involucres with (2–)3–4 subequal series of herbaceous phyllaries, white rays, long style-branch appendages, and cylindric cypselae. The species mostly have been previously treated within Aster.
Cronquist, A. 1948. A revision of the Oreastrum group of Aster. Leafl. W. Bot. 5: 73–82. Nesom, G. L. 1993d. The genus Oreostemma (Asteraceae: Astereae). Phytologia 74: 305–316.