Oreostemma

Greene

Pittonia 4: 224. 1900

Common names: Mountaincrown
Etymology: Greek oreo, mountain, and stemma, crown
Basionyms: Oreastrum Greene
Treatment appears in FNA Volume 20. Treatment on page 359. Mentioned on page 18, 362, 365.
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.

Distribution

w United States.

Discussion

Species 3 (3 in the flora).

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.

Lower Taxa

Key

1 Plants 2–7 cm; stems, phyllaries, and often leaves sparsely villous to glabrate, densely short-stipitate-glandular; leaf blades linear Oreostemma peirsonii
1 Plants 4–70 cm; stems, leaves, and phyllaries glabrous or villous, eglandular; leaf blades oblanceolate > 2
2 Stems, leaves, and phyllaries villous to glabrate, at least some hairs always perceptible on distal stems and proximal portions of phyllaries; phyllaries herbaceous or slightly tawny-indurate proximally, outer 0.8–1.2 mm wide proximally, 1-nerved Oreostemma alpigenum
2 Stems, leaves, and phyllaries glabrous; phyllaries strongly indurate-stramineous proximally, outer 1.5–2 mm wide proximally, 3-nerved (nerves separating phyllary into 4 longitudinal bands) Oreostemma elatum