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.)

The name Gentiana linearis var. lanceolata A. Gray was applied originally to plants referable to G. linearis, although the name G. rubricaulis was cited in synonymy. The name G. linearis var. latifolia was applied originally only to G. rubricaulis, but both of these names were applied subsequently to both that species and relatively wide-leaved specimens of G. linearis. This confusion has been responsible in some cases for the rejection of specific status for G. rubricaulis, and for erroneous reports of G. rubricaulis in New York and Vermont. Reports from Nebraska were based on an old misidentification of G. puberulenta. Reports from Saskatchewan were also based on misidentified specimens. Reports of G. rubricaulis in Maine and New Brunswick are correct, although these populations are disjunct by about 775 km from the easternmost populations in Ontario.

In marked contrast to all other species of Gentiana in eastern and central North America, including G. linearis, the involucral leaves of this species are strongly ascending and somewhat conduplicate as well as being wider, and envelop the proximal portion of the flower cluster.

In the vicinity of Lake Superior, where the ranges of Gentiana rubricaulis and G. linearis overlap, these species maintain their distinctness, with G. rubricaulis occurring in calcareous soils and G. linearis in granitic and similar strongly acid soils (J. S. Pringle 1968). A few hybrids of G. rubricaulis with G. andrewsii, which is likewise a calciphile, are known. These hybrids have been designated G. × grandilacustris J. S. Pringle.

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