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.)

Varieties 2 (2 in the flora).

Gentiana affinis is highly variable, and some authors have divided it into several species, or have recognized more varieties than the two accepted in this flora. N. H. Holmgren (1984b) speculated that further studies might disclose patterns that would warrant the recognition of additional infraspecific taxa in G. affinis. From studies for the present and earlier works, however, only two varieties appear to be well differentiated, and even these intergrade in Idaho, Montana, Oregon, and northern California, especially in Del Norte County, California. Despite the very different vegetative aspects of the extremes, which sometimes occur more or less sympatrically, intergradation is so extensive that the recognition of these taxa as distinct species seems inappropriate. The treatment of G. affinis presented here, although based on an independent approach involving the study of numerous specimens, is essentially in agreement with that of Holmgren and is supported by biometric analyses by J. R. Spence (unpubl.), which confirmed the intergradation between var. affinis and var. ovata.

Only var. affinis approaches the range of Gentiana puberulenta. Large plants of G. affinis generally differ from small plants of G. puberulenta in the proportionate lengths of the corolla lobes and the free portions of the plicae. In G. affinis, the lobes are less than two times as long as the free portions of the plicae; in G. puberulenta they are generally two or more times as long.

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