21. Gentiana andrewsii Grisebach in W. J. Hooker, Fl. Bor.-Amer. 2: 55. 1837.
[E F]
Bottle or fringed bottle or prairie closed gentian, gentiane d’Andrews ou close
Dasystephana andrewsii (Grisebach) Small; Pneumonanthe andrewsii (Grisebach) W. A. Weber
Herbs perennial, 1–12 dm, glabrous or rarely puberulent. Stems 1–20, terminal from caudex, decumbent to erect. Leaves cauline, ± evenly spaced; blade elliptic-oblong to lanceolate or narrowly ovate, 3–16 cm × 10–50 mm, apex acuminate. Inflorescences 1–25-flowered heads, often with additional flowers at 1–6(–9) nodes or on short branches. Flowers: calyx 9–29 mm, lobes lanceolate to ovate or occasionally oblanceolate, 2–15 mm, margins ciliate; corolla blue, white, or rarely rose-violet, tubular, completely closed, 28–45 mm, lobes reduced to a mucro or ± triangular, 0.5–2(–3) mm, free portions of plicae oblong, shallowly and nearly symmetrically bifid, summit truncate, erose; anthers connate. Seeds winged.
Varieties 2 (2 in the flora): North America.
Gentiana andrewsii is the only species of Gentiana in which the plicae of the corolla are distinctly longer than the lobes.
Gentiana andrewsii has often been reported outside its actual range. Although the epithets of some of the species that have been confused with or considered inseparable from G. andrewsii have priority, the familiar name G. andrewsii is often misapplied, sometimes because it is assumed that any “closed gentian” is G. andrewsii. As G. clausa was not distinguished from G. andrewsii in standard floras prior to 1950, reports from the northeastern United States based on specimens identified before 1950 should be considered doubtful if the specimens have not been reexamined. Old reports from the southern Appalachians are also questionable because G. austromontana was not recognized until 1964. Some reports from the southeastern and south-central United States and along the Atlantic seaboard have been based on specimens of G. saponaria. True G. andrewsii is distinguishable as the only Gentiana species in which the corolla plicae distinctly exceed the minute lobes. The fringed tip of the completely closed corolla, at first white, soon turning reddish brown, is an excellent field mark for distinguishing G. andrewsii from G. clausa. In G. clausa, the summit of the intact corolla appears completely blue (in the typical color form), and the plicae are concealed. Gentiana andrewsii grows in calcareous soils and G. clausa in noncalcareous soils.
Because of this ecological separation, there are only a few records of hybridization between Gentiana andrewsii and G. clausa. In the tall-grass prairies, G. andrewsii hybridizes with G. flavida, producing G. × pallidocyanea J. S. Pringle, and with G. puberulenta, producing G. × billingtonii Farwell (as species). Northward, it occasionally hybridizes with G. rubricaulis, producing G. × grandilacustris J. S. Pringle, and in the southeastern part of its range it hybridizes with G. saponaria.
