Platanthera obtusata
Platanthera orbiculata
blunt-leaf bog-orchid, blunt-leaf rein-orchid, blunt-leafed rein orchid, bluntleaf orchid, northern small bog orchid, one-leaf rein-orchid, small northern bog-orchid
large round-leaf orchid, large round-leaf rein orchid, lesser roundleaf orchid, round-leaf bog-orchid, round-leaf orchid
1(–2, rarely), spreading-ascending on base of stem;
bracts 0(–1, rarely);
blade linear-oblanceolate, elliptic, or broadly obovate, 3.5–15 × 0.8–5 cm.
2, in subequal basal pair lying on ground;
bracts (very rarely, 0–)1–6, scattered along stem;
blade broadly elliptic to orbiculate or oblate, 5–21 × 3–22 cm.
lax.
lax to dense.
resupinate, not showy, greenish white to yellowish green;
corolla commonly whiter than calyx;
lateral sepals reflexed;
petals rhombic, lanceolate-falcate, margins entire;
lip descending, linear, narrowly lance-rhombic, or linear-hastate, with median basal thickening, unlobed, 2.5–8(–10) × less than 1–2 mm, margins entire;
spur slenderly conic, 3–8(–10) mm;
rostellum lobes directed forward, wide-spreading, rounded-angular;
pollinaria straight;
pollinia remaining enclosed in anther sacs;
viscidia orbiculate;
ovary rather slender to stout, mostly 3–10 mm.
resupinate, rather showy;
calyx mostly greenish white;
corolla mostly white;
lateral sepals reflexed to somewhat spreading;
petals lanceolate-falcate, margins entire;
lip descending to somewhat reflexed, linear-oblong to linear-lanceolate, without basal thickening, 7–17 × 1–2.5 mm, margins entire;
spur slenderly clavate, 14–27 mm;
rostellum lobes directed strongly forward, wide-spreading, angular;
pollinaria nearly straight, 3–4.5(–4.8, very rarely) mm;
pollinia remaining enclosed in anther sacs;
viscidia orbiculate;
ovary slender to rather stout, mostly 10–26 mm.
= 42, 63 (American, as Habenaria obtusata), 126 (Eurasian, as Habenaria obtusata).
= 42.
Platanthera obtusata
Platanthera orbiculata
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.)
The key will permit determination of most specimens of Platanthera orbiculata and P. macrophylla. More precise discrimination of ambiguous specimens is possible by use of the formula from A. H. Reddoch and J. M. Reddoch (1993): spur length + (2 × pollinarium length), which for P. orbiculata is less than 38 and for P. macrophylla is equal to or greater than 38.
Considerable variation in size and shape of leaves occurs, and although to some extent regional in nature, intergradation is complete; recognition of infraspecific taxa is unwarranted. A few collections from isolated areas on the Pacific Coast of Canada are noteworthy, however. Those are small, few-flowered plants with rather narrow leaves borne alternately or suboppositely toward the base of the stem, as in some Asiatic species. They are in some respects very similar to Platanthera freynii Kränzlin, an Asiatic species distinguished primarily by its abruptly narrowed petals, in contrast to the generally broader, but variable, petals in North American plants. These western plants warrant further study to establish their identity and to elucidate relationships between North American and Asiatic species.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
OR
SW CO Wildflowers- Local floras:
BC, 
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MI Flora, 
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PNW Herbaria, Turner Photog. 
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