Marsh or rangers’ gentian, rose-gentian

Gentiana acuta Michaux, Fl. Bor.-Amer. 1: 177. 1803; G. amarella Linnaeus var. plebeia (Chamisso ex Bunge) Hultén; G. amarella var. acuta (Michaux) Herder; G. strictiflora (Rydberg) A. Nelson; Gentianella acuta (Michaux) Hiitonen; G. strictiflora (Rydberg) W. A. Weber

Herbs annual, (2–)4–50(–80) cm. Stems erect, simple or branched distally, sometimes also with long branches from near base. Leaves: basal present or withered by flowering, blades spatulate to elliptic-oblong, 6–50 × 3–20 mm; cauline blades ovate to oblong-lanceolate, 8–60 × 2–20 mm. Inflorescences terminal and axillary, dichasial cymes, lateral flowers in smaller cymes or axillary flowers solitary; pedicels (0–)8–25(–50) mm. Flowers (4- or)5-merous; calyx 4–13(–18) mm, lobes all connate proximally to ± the same level, linear to lanceolate, subequal or occasionally distinctly unequal but not foliaceous, 2–10(–15) mm; corolla deep to pale violet-blue to purplish pink (often bluer dried than fresh), pale yellow, or white, tubular to narrowly campanulate, 7–21 mm (proximal flowers often much smaller than distal), lobes ascending to spreading, ovate-triangular, 3–5.5 mm, apex obtuse to acute, with a fringe of trichomes near base of each lobe (fringes occasionally poorly developed, or absent in small flowers); ovary sessile. 2n = 18, 36.

Flowering summer–early fall. Mesic to wet meadows, fens, prairies, clearings, roadsides, open woods, cliffs, beach ridges, tundra, generally calcareous soils; 0–4100 m (restricted to higher elevations southward); Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Maine, Minn., Mont., Nev., N.Mex., N.Dak., Oreg., S.Dak., Utah, Vt., Wash., Wyo.; Mexico (Durango, Nuevo León, Sinaloa); e Asia.

An outlying population of subsp. acuta in Vermont, historically much collected, is no longer extant. Records for Nunavut are from Akimiski Island in James Bay only.

Subspecies acuta and its homotypic synonyms were formerly associated only with the North American (including Mexican) representatives of Gentianella amarella, but in recent decades, the taxon has generally been circumscribed to include the plants of this complex in eastern Asia south to central China.

Some authors do not separate subsp. acuta from subsp. amarella, whereas others treat it as a distinct species. Morphologically, subsp. acuta is weakly differentiated from subsp. amarella. The flowers of the plants in much of Europe average larger when flowers in similar positions on plants of similar size are compared, but in all such comparisons there is extensive overlap in flower size. Other distinctions reported in earlier literature have been found not to be consistent upon examination of specimens from throughout the range of the species in the broad sense (M. L. Fernald 1917b; studies for this flora). Specimens from Scandinavia examined in studies for this flora appeared indistinguishable from North American plants. Presumed differences in ploidy level have probably influenced some authors’ acceptance of the taxon acuta at specific or subspecific rank, but chro­mosome counts remain too few to indicate adequately the ranges of plants with the respective ploidy levels. Counts of 2n = 18 have been reported from Québec and California, and 2n = 36 has been reported from Manitoba, Iceland, Spain, and Sweden.

Historically, the North American representatives of Gentianella amarella have variously been divided into several species, as well as subspecies and varieties, based largely on plant stature and branching, but also considering four- versus five-merous flowers, corolla color, and other characters, as well as habitats. J. E. Weaver and F. E. Clements (1929) and J. M. Gillett (1957) concluded from their studies of this species that much of the morphological diversity in North America represented responses to interactions of seasonal phenomena with the time of seed germination and with light and shade, density of surrounding vegetation, and other conditions of the diverse macro- and microhabitats in which this taxon is found. Their conclusion was subsequently accepted by N. H. Holmgren (1984b), who included all of the North American taxa that had been segregated from this species or treated as sub­species or varieties of it in the synonymy of undivided G. amarella. In studies for this flora, it was found that plants of comparable height but differing in branching pattern, some with long branches from the base and others with only short, distal branches, were often present in the same population and included in the same collections. Plants with relatively closely spaced nodes and strongly ascending branches have been given the epithet strictiflora in various combinations, but complete intergradation appears to connect the extremes and little if any correlation is evident between plant habit and geographic distribution. The epithet plebeia has been applied to plants relatively low in stature, with few branches and wide leaves, but this distinction has generally been rejected in recent literature. Such plants often occur in the same areas as subsp. acuta in the narrow sense. They have sometimes been assumed to be more or less isolated reproductively through genetically determined earlier flowering, but most such specimens seen in studies for this flora had been found in flower no earlier than specimens not exhibiting such morphology. Experiments involving transplants or similar techniques would be of interest, but no such studies have been reported.