Flora of North America species comparison

Gentiana puberulenta is evidently extirpated from Ontario, Louisiana, Maryland, and New York, where outlying prairie communities have largely been eliminated by agricultural and urban expansion.

The name Gentiana puberula Michaux 1803, not Franchet 1890, and the homotypic synonym Dasystephana puberula (Michaux) Small have long and often been misapplied to this species but are typified by a specimen of G. saponaria.

Some small plants of Gentiana puberulenta appear similar to G. affinis var. affinis, but only a few specimens appear actually to be hybrids between these species. Where their ranges approach each other, the flowers of G. affinis are generally much smaller than those of G. puberulenta, and the corolla lobes of G. affinis are generally less than twice as long as the free portions of the plicae, whereas those of G. puberulenta are more than twice as long. The flower size of G. affinis var. ovata more closely approaches that of G. puberulenta, but in that variety, the range of which does not overlap that of G. puberulenta, the leaves are usually ovate to elliptic rather than narrowly oblong-lanceolate, and the distal internodes are often about as long as or longer than the leaves, in contrast to the proportionately shorter internodes of G. puberulenta. For further guidance in distinguishing between G. puberulenta and G. affinis, see discussion under 13. G. affinis.

Hybrids of Gentiana puberulenta with the strikingly dissimilar G. andrewsii, constituting G. × billingtonii Farwell (as species), and with G. flavida, constituting G. × curtisii J. S. Pringle, occur in the tall-grass prairies. Hybrids with G. saponaria formerly occurred in western Maryland.

(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.)