Colorado frasera

Swertia coloradensis C. M. Rogers, Madroño 10: 108. 1949

Herbs perennial, 1.5–2.5 dm; stems and adaxial leaf surfaces puberulent. Stems 1–several. Leaf blades narrowly white-margined; basal narrowly oblanceolate, 4–17 × 0.4–2 cm; cauline leaves opposite, distal blades linear-oblanceolate. Inflorescences diffuse, 5–30 cm wide, branching near base of main stems. Flowers: calyx 7–13 mm; corolla white to cream, usually rather sparsely purple-dotted, 7–10 mm, lobes oblong-obovate, apex abruptly acuminate; androecial corona poorly developed, usually comprising erose scales 0.2–1 mm and few trichomes; style slender, distinct; nectaries and foveae 1 per corolla lobe, foveae opening distal to nectary, into an orbiculate to elliptic-oblong differentiated area on the corolla lobe, rim ± fringed all around.

Flowering summer. Grasslands, open pine-juniper woods, often around sandstone or limestone outcrops; of conservation concern; 1200–1700 m; Colo., Okla.

Frasera coloradensis is endemic to Baca, Bent, Las Animas, and Prowers counties in southeastern Colorado and Cherokee County in adjacent Oklahoma.

To a greater degree than other Frasera species, F. coloradensis forms relatively large clusters of divergent rather than erect stems. Otherwise, it is somewhat similar to F. puberulenta, from which it is separated by about 1500 km. Frasera coloradensis has corymboid inflorescences, about as wide as long, with branches or pedicels arising in pairs at each node of the main axis, and many long leaves in the inflorescences; F. puberulenta has more elongate inflorescences, usually with branches and/or pedicels arising in whorls from some nodes of the main axis, and few if any large leaves in the inflorescences. In F. puberulenta the nectary is more deeply pocketed. Frasera coloradensis is also somewhat similar to F. albomarginata var. induta. It differs in its opposite rather than proximally whorled leaves, its larger leaves within the inflorescence, and the highly dissimilar shape of the differentiated areas on the corolla lobes.

Frasera coloradensis is in the Center for Plant Conservation’s National Collection of Endangered Plants.