White frasera

Swertia montana (Mulford) H. St. John, Amer. Midl. Naturalist 26: 16. 1941; Leucocraspedum montanum (Mulford) Rydberg

Herbs perennial, 2.5–8 dm, glabrous or stems and leaf bases minutely puberulent. Stems 1–several, with several rosettes. Leaf blades white-margined; basal narrowly spatulate-oblanceolate to lanceolate, 7–30 × 0.5–1.5 cm; cauline leaves opposite, blades narrowly lanceolate to linear. Inflorescences narrow, 1.5–4 cm wide, dense. Flowers: calyx 3–6(–8) mm; corolla white to cream, unmarked, 5–9 mm, lobes elliptic-ovate, apex rounded, apiculate; androecial corona scales obovate-oblong, 1–2 mm, margins nearly entire to deeply lacerate or fringelike; style slender, distinct; nectaries and foveae 1 per lobe, foveae opening into an elliptic-obovate to suborbiculate differentiated area on the corolla surface, rim ± evenly fringed all around.

Flowering late spring–summer. Dry mountain mead­ows, sagebrush slopes, open pine woods; 1200–2000 m; Idaho.

Frasera montana is endemic to the mountains of western Idaho.

Frasera montana appears to be closely related to F. albicaulis and might be treated as another variety of that species, but its proportionately wide corolla lobes with rounded rather than acute to acuminate apices, reminiscent of the petals of apple blossoms, give the flowers of this attractive species a distinctive appearance. The differentiated areas on the corolla surface into which the foveae open are elliptic to nearly round and are proportionately shorter than those of any variety of F. albicaulis. Frasera montana might most readily be confused with F. albicaulis var. idahoensis, which likewise usually has unspotted corollas, but it can be distinguished not only by the shape of its corolla lobes but also by the differentiated areas on its corolla lobes with rims that are more or less evenly long-fringed all around; those of all varieties of F. albicaulis are distally more shallowly or not fringed. The androecial corona scales of both species are variable, but those of F. montana are generally cleft more or less longitudinally, if at all, whereas those of F. albicaulis var. idahoensis (but not all varieties of F. albicaulis) usually bear lateral as well as terminal lobes or fringes.