Yukon fringed gentian

Gentianella detonsa (Rottbøll) G. Don subsp. yukonensis J. M. Gillett, Ann. Missouri Bot. Gard. 44: 215. 1957

Herbs 0.5–6 dm. Stems except those of smallest plants with branches or peduncles arising from nodes distinctly above base, occasionally also from base. Leaf blades: basal leaves in a distinct rosette, blades oblong to oblanceolate, apex obtuse to subacute; cauline lanceolate to linear, apex acute. Flowers: outer calyx lobes distinctly longer than inner, lance-ovate, apex acuminate to attenuate, inner lanceolate, apex acute to short-acuminate; corolla 12–50 mm, lobes oblong to elliptic-lanceolate, 0.5+ times as long as tube, margins distinctly although sometimes sparsely fringed proximally, dentate toward apex, apex acute; gynophore short, thick. Seed coat papillate only toward ends.

Flowering summer. Tundra, wet meadows and sub­alpine heathland, open woods, sandy or gravelly soils; 100–500 m; Yukon; Alaska.

Subspecies yukonensis is endemic to the watershed of the Yukon River and its tributaries.

Subspecies yukonensis combines character states associated with both subsp. detonsa and subsp. raupii, but it cannot satisfactorily be included in either. Differences in branching pattern have been overstated. Branches or peduncles frequently arise from the base in subsp. yukonensis as well as in subsp. raupii, and plants not branched from the base, although often one-flowered, are frequent in subsp. raupii as well as in subsp. yukonensis. Occasional plants from the range of subsp. raupii resemble plants from the Yukon River basin, but subsp. raupii usually has a stouter aspect than subsp. yukonensis, and plants of subsp. raupii of comparable stature usually have more basal branches that closely approach the main axis in height and stem diameter.

Subspecies yukonensis usually has a well-developed rosette of oblanceolate leaves wider than the cauline leaves, the rosette being separated from the cauline leaves by a distinct internode, whereas the basal rosette of subsp. raupii is usually less well developed, and its leaves are gradually transitional to the proximal cauline leaves. The corolla lobes of subsp. yukonensis distally taper gradually to an acute apex, whereas those of subsp. raupii are shaped more like an old-fashioned keyhole, proximally oblong, rather abruptly widening to an ovate to suborbiculate distal portion, rounded at the apex.

Because of its widely separated, linear cauline leaves, subsp. yukonensis is more similar in aspect to the taller plants of subsp. detonsa than to subsp. raupii. Subspecies yukonensis differs from subsp. detonsa in its obtuse cauline leaf apices and proximally fringed rather than merely dentate corolla-lobe margins and usually has more basal leaves.

Reports of Gentiana barbata Froelich from Alaska (E. Hultén 1968) were based on specimens of Gentianopsis detonsa subsp. yukonensis. The Eurasian taxon formerly called Gentiana barbata has sometimes been included in Gentianopsis detonsa but is usually treated as a distinct species, Gentianopsis barbata (Froelich) Ma. Were these taxa considered conspecific, the epithet detonsa would have priority over barbata.