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.)

Plants of Gentiana sceptrum with ascending, narrowly lanceolate leaves conspicuously exceeded by the distal internodes have been called G. menziesii. Plants with spreading, elliptic to ovate, more closely spaced leaves have been called G. sceptrum var. cascadensis, although that variant might more appropriately be considered nomenclaturally typical. Studies for this flora have indicated that the extremes are connected by many intermediates, and that little correlation exists between leaf shape and geographic distribution, or between leaf shape and the other traits by which the segregates have been characterized, such as stature, erectness of stems, or numbers and sizes of flowers. Even within a relatively limited area, such as Vancouver Island, British Columbia, or Humboldt County, California, plants can be found with leaves ranging from narrowly lanceolate to widely elliptic.

Small plants with strongly decumbent stems, found at a few localities at or near the coast in California and southern Oregon, have been called Gentiana sceptrum var. humilis. Spathaceous calyces occasionally occur in these plants. Such plants are not recognized taxonomically here because larger plants approaching typical G. sceptrum have been found at the same localities or nearby, but they should be given further study.

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