Flora of North America species comparison

Varieties 2 (2 in the flora).

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.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

The name Gentiana alba Muhlenberg has often been applied to this species. Uncertainty had long persisted, first as to whether the name G. alba was validly published by G. H. E. Muhlenberg in 1813, then, after that publication had been deemed invalid, whether it was validated by T. Nuttall in 1818. A group of nomenclatural authorities considered this issue on behalf of this flora and concluded that neither of those publications of the name G. alba had been valid, and that G. flavida A. Gray was the earliest validly published name for this species (K. N. Gandhi, pers. comm.).

Outlying eastern populations of Gentiana flavida in North Carolina, Pennsylvania, and West Virginia are no longer extant, and the continued existence of other peripheral populations in isolated prairie remnants is precarious. Reports from Manitoba have been based on misidentified G. rubricaulis. A report from Maryland was based on the misreading of a label of a specimen actually from Indiana (studies for this flora).

In contrast to those of the other species of Gentiana in the flora area, with the exceptions of G. clausa and G. latidens, the calyx lobes of G. flavida spread widely, with keels like shelf brackets decurrent on the tube.

Morphological variation in Gentiana flavida should be given further study. According to J. T. Curtis (1959), plants of this species from the northern part of its range, as seen in the field, appear distinctly different in inflorescence form from plants native farther south.

In the tall-grass prairies, Gentiana flavida hybridizes with G. andrewsii, producing G. × pallidocyanea J. S. Pringle, and G. puberulenta, producing G. × curtisii J. S. Pringle. Reports of G. flavida with the corollas distally lilac have been based on plants derived from such hybridization, probably through backcrossing.

(Discussion copyrighted by Flora of North America; reprinted with permission.)