Flora of North America species comparison

In addition to the color forms noted in the description, a bicolored form of Gentiana calycosa in southwestern Washington has blue corollas with the center of the distal third of the corolla lobes, including the short-acuminate tip, white.

Gentiana calycosa varies greatly in stature and in the size of its leaves and flowers. Most plants of G. calycosa from the Pacific coastal region, including western Washington and Oregon and most of California, have tubular calyces with well-developed, ovate to elliptic lobes varying in size but usually 3–8 mm. In Canada such plants also prevail east to Alberta; southward, in the United States, they also prevail in Wyoming. From eastern Washington and Oregon to Idaho and parts of Montana, and in Nevada and Utah, the calyces are usually cleft and spathaceous, with the lobes much reduced, less than 3.5 mm, and linear, or vestigial or absent. Extreme forms of such plants have been called subsp. or var. asepala. Because of the sporadic rather than continuous distribution of such forms, the intergradation, especially in the vicinity of Mount Rainier, Washington, and in parts of Montana, where populations may include plants approaching both extremes along with intermediates, and the lack of correlation with other morphological variation, such plants are not distinguished taxonomically in this flora. To some extent their occurrence appears to be correlated with warmer, drier regions, and may be influenced by the habitat.

In most of its range, Gentiana calycosa grows in wet alpine meadows and similar moist habitats, but in the western Cascades it almost always grows in drier, north-facing sites on rocky slopes and cliffs. (T. Harvey, pers. comm.). Plants of G. calycosa in well-drained rocky slopes were distinguished as G. saxicola English (1934), not Grisebach (1838). According to C. S. English (1934), these plants differ from those of wet alpine meadows in having erect rather than decumbent stems; internodes mostly about as long as the leaves rather than distal internodes much longer than the leaves; and spreading rather than erect calyx lobes, which are larger and proportionately wider. According to Harvey, in contrast, the stems of the plants from the drier, rocky sites in the western Cascades are more likely to have decumbent stems. No consistent association of these morphological variations or correlation with geographic distribution was substantiated in the studies for this flora, but further study would be desirable, as molecular phylogenetic studies (A. Favre, pers. comm.) suggest that taxonomic recognition of these ecotypes might be appropriate.

There are records of hybrids of Gentiana calycosa with G. affinis var. affinis and G. newberryi var. newberryi.

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