Flora of North America species comparison

The rare Eurasian Platanthera obtusata subsp. oligantha (Turczaninow) Hultén differs from the North American subsp. obtusata in its smaller dimensions and rhombic-lanceolate lip. It is also said to be densely few-flowered, although some Siberian material is comparable to American plants. Supposedly intermediate plants are reported from Alaska, and much material from that area is reduced in stature and with smaller flowers than typical of American plants. In most cases, however, lips are relatively slender, and the plants seem merely to be stunted by their environment. One or two collections from the Alaskan Peninsula and Aleutians, however, seem entirely referable to subsp. oligantha with dense, few-flowered inflorescences of very small flowers with rhombic-lanceolate lips and shorter curved spurs. Eurasian plants are reported to be hexaploid or perhaps sometimes triploid, and if the apparent ploidy differences delimit the taxa, then it should be possible to unequivocally identify Alaskan plants.

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

Platanthera convallariifolia is commonly reported from the Aleutians and adjacent coastal Alaska based on short, very broad-leaved plants with rather large flowers in dense, thick inflorescences. Those plants, however, apparently represent robust, maritime phenotypes of P. huronensis or in some cases P. stricta or P. dilatata comparable to those seen in Piperia elegans and Spiranthes romanzoffiana. In fact, typical Asiatic Platanthera convallariifolia is a slender-leaved plant entirely comparable in habit to P. huronensis. The two species are very similar, and they share a tetraploid chromosome number. Typical Asiatic P. convallariifolia is characterized by a linear lip and clavate spur about 2/3 to nearly the length of the lip. The lip occasionally varies to slightly lanceolate and the spur to somewhat saccate. The column appears somewhat broader than in P. huronensis, and viscidia also are apparently rather broad. A few specimens from the Aleutians and Alaskan peninsula exhibit these floral characteristics. Vegetatively, however, some Alaskan material is distinctive in the position and orientation of the leaves. In floral and vegetative characters, Alaskan plants furthermore intergrade with P. huronensis. Whether Alaskan plants are truly referable to P. convallariifolia is uncertain, and the status of the Asiatic species also needs study. Both P. convallariifolia and the Alaskan plants here referred to it appear to combine features of P. huronensis and P. stricta. Platanthera convallariifolia may have arisen through hybridization of these two species, or of P. stricta and P. dilatata, thus accounting for the difficulty in identification. The description presented here is based on few Alaskan plants and is apt to be too restrictive; therefore the poor understanding of the plant makes the present delimitation and distinctions from P. huronensis rather arbitrary.

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