Large-flowered fringed or grand fringed gentian

Gentianella macrantha D. Don ex G. Don, Gen. Hist. 4: 179. 1837; Gentiana grandis (A. Gray) Holm; G. superba Greene; Gentianella detonsa (Rottbøll) G. Don subsp. superba (Greene) J. M. Gillett

Herbs annual, 1–9 dm. Stems simple or with branches or peduncles arising from nodes distinctly above base. Leaves: basal usually persistent at flowering, blades spatulate to oblanceolate, 0.8–8 cm × 2–20 mm, apex rounded or obtuse; cauline blades elliptic to narrowly lanceolate or linear, 2–9 cm × 3–23 mm, apex obtuse (proximal leaves) to acute. Peduncles 6–35 cm. Flowers 1–many; calyx 18–55 mm, keels minutely granular-scabridulous, all or at least outer lobes 1.5–2.5 times as long as tube or longer, lobes nearly equal in shape and size, ovate-lanceolate, apex of outer lobes acuminate to attenuate, apex of inner lobes acuminate; corolla proximally white with violet-blue to violet veins, distally violet-blue to violet, 40–80 mm, lobes proximally oblong, expanding into rhombic distal portion, that is, with apex ± acute, 18–53 × 11–25 mm, margins with fringes to 5 mm on the sides, dentate around apex; ovary distinctly stipitate. Seeds papillate, not winged.

Flowering fall. Open woods, roadsides; 1500–2800 m; Ariz.; Mexico (Chihuahua, Durango, Sonora, Zacatecas).

In the flora area, Gentianopsis macrantha is known only from extreme southern Arizona. Specimens from New Mexico have been reidentified as G. thermalis.

Gentianopsis macrantha is distinguished from large-flowered plants of G. thermalis by its combination of stems that are simple or branched only well above the base; all four calyx lobes distinctly longer than the tube, usually more than 1.5 times as long; a more gradually flaring corolla tube, which is obconic rather than more nearly cylindric; rhombic distal portions of the corolla lobes, which widen above the base and taper from below the middle to a nearly acute apex, being shaped somewhat like the blade of a traditional mason’s trowel rather than being ovate to orbiculate; and the pale portion of the corolla that extends to the proximal part of the lobes, in which the veins are sharply outlined in deep violet-blue or violet, whereas in G. thermalis the corolla lobes and upper part of the tube are usually deep blue throughout. A few specimens of G. thermalis, mostly from Arizona and New Mexico, are similar to G. macrantha in flower size or have calyx lobes that are relatively long in proportion to the tube and might be considered intermediate between these species. In occasional specimens of G. thermalis, mostly from Utah and Arizona, the pale zone of the corolla extends into the proximal portion of the lobes as in G. macrantha. Such specimens have sometimes been identified as G. macrantha but can generally be distinguished by the branching pattern and/or the corolla-lobe shape.

J. M. Gillett (1957) has suggested that the name Gentiana macrocalix Lexarza may have been applied to Gentianopsis macrantha, in which case, at species rank, the epithet macrocalix would have priority over macrantha. No type specimen of the name Gentiana macrocalix is known, but from studies for this flora, this name is assumed to have been applied to a Mexican taxon not occurring in the flora area.