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.)

In contrast to the deep green stems and leaves of Gentiana prostrata, the vegetative parts of G. fremontii are much paler. G. Engelmann (1879) described plants of G. fremontii as having a pale, sickly appearance, and J. A. Ewan annotated specimens as having been yellowish when seen in the field, reminiscent of a fungus or broomrape (Aphyllon or Orobanche). This suggests that mycorrhizal symbiosis is especially significant in this species, but its trophic ecology has not been studied.

Gentiana fremontii differs further from G. prostrata in having obovoid capsules less than twice as long as wide, generally not fully exserted from the marcescent corolla, narrowly winged distally along the sutures, with valves that eventually separate nearly to the base, whereas the capsules of G. prostrata are compressed-cylindric, more than twice as long as wide, often fully exserted at maturity, not winged, with the valves separating only above the middle. Also, although both species vary in this respect, G. fremontii more often has the flower parts in fives.

The names Gentiana aquatica Linnaeus and Chondrophylla aquatica (Linnaeus) W. A. Weber have often been applied to this species. Gentiana fremontii, although similar to the Siberian and Chinese G. aquatica, appears to differ consistently in the wider, more conspicuous white margins of its leaves, longer and proportionately narrower mid-cauline leaves, usually white rather than blue corollas, and corolla plicae that generally have jagged rather than entire summits. The illegitimate name G. humilis Steven 1812, not Salisbury 1796, has also been applied to G. fremontii, but the North American plants are not now considered conspecific with the type from Azerbaijan.

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