Platanthera obtusata (Banks ex Pursh) Lindley

Blunt-leaf orchid

The specific epithet obtusata is the Latin meaning "blunted," in reference to the blunted leaf of this species.

Photo courtesy of Mark Larocque

DESCRIPTION: Plant glabrous, arising from a cluster of fleshy, thickened roots, 5-25 cm tall (including inflorescence). Leaf 1, basal, obovate to oblanceolate, obtuse, 4-15 cm long and 1-4.5 cm wide, keeled. Inflorescence a lax raceme, 10-30 flowered; flowers green to yellowish- or whitish-green, each flower subtended by a lance-linear, acuminate bract. Lateral sepals lanceolate to elliptic, 3-5 mm long and 2-3 mm wide, reflexed, colored as flowers; dorsal sepal broadly ovate, 2-4.5 mm long and 2-4 mm wide, connivent with petals over the column, colored as flowers. Petals lanceolate, 2.5-5 mm long and 1-2 mm wide, connivent with dorsal sepal over the column. Labellum linear-lanceolate and acute, 4-8 mm long and 0.5-2 mm wide, colored as flowers; base of labellum with a two small auricles and an acute nectar spur projecting behind, 4-7.5 mm long.

Platanthera obtusata could perhaps be confused with P. clavellata, as both species are found in swampy or boggy areas and have only one leaf. The two are easily separated by the shape of the labellum: the labellum is narrow-lanceolate and acute in P. obtusata, but is oblong and tridentate in P. clavellata.

Platanthera obtusata could also perhaps be confused with either of the two species of Malaxis, which also have one leaf and my occur in the same habitat. P. clavellata is easily separated, however, by its elongate nectar-spur, which is absent in Malaxis.

Platanthera obtusata is typically found in sphagnous, swampy areas, usually under Thuja or Picea. In northern Wisconsin, P. obtusata can be very common in such habitats.

June 15-September 1.

Platanthera obtusata is pollinated by mosquitos (Stoutamire 1968, Thien & Utech 1970) and small pyralid moths (Voss & Riefner 1983). The research by Thien and Utech was conducted while Leonard Thien was at the University of Wisconsin.

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