Flora of North America species comparison

Primula incana is usually heavily farinose, at least when young, and has relatively tall scapes and tight umbels of homostylous flowers. As with some species of the genus, anthesis often begins before the scape is fully elongated; plants at first are quite small, but elongate throughout anthesis and typically become relatively tall and lanky in age. This has led to confusion with other arctic species, especially P. stricta, which has considerably less farina, a shorter scape, and a more maritime distribution. In fruiting stage, P. incana has been confused with P. laurentiana, which has looser umbels throughout anthesis, larger flowers, and a more eastern distribution. Primula incana generally replaces P. laurentiana to the west and south of Hudson Bay. The single octoploid count for P. incana is questionable; the species appears to be consistently hexaploid in other counts.

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

Primula borealis varies in height, leaf morphology, and amount of farina, characters that are all influenced by ecology and phenology. Exposed dune populations are often composed of depauperate individuals; inland populations in protected or nutrient-rich sites can contain individuals over 10 cm in height with more flowers. Younger individuals are almost always farinose; farina sometimes disappears later in the growing season. The species characteristically shows a broad corolla and a full symmetrical umbel on a relatively short scape giving a top-heavy appearance at anthesis. Involucral bracts are saccate or gibbous, in comparison to the often sympatric species P. anvilensis and P. nutans, with plane and auriculate bracts, respectively. Inland populations previously identified as P. borealis should generally be placed under P. mistassinica, which can be distinguished by its more delicate appearance and usually efarinose vegetative parts. Plants from near Kotzebue, Alaska, called P. mistassinica by L. A. von Chamisso and D. F. L. von Schlectendahl (1826–1836) belong to P. borealis.

In the Russian Far East and Japan, it is difficult to separate the North Pacific complex centered on Primula modesta Bisset & S. Moore (including P. ajanensis E. A. Busch, P. fauriei Franchet, P. kawasimae H. Hara, and P. matsumurae Petitmengin) from the complex centered on P. borealis. These show morphological similarities; they differ in chromosome number. No recent comprehensive systematic work has been done on the North Pacific representatives of sect. Aleuritia; molecular and morphometric analyses may help clarify phylogenetic relationships and taxonomy of these taxa.

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