Platanthera dilatata

(Pursh) Lindley ex L. C. Beck

Bot. North. Middle States, 347. 1833.

Basionym: Orchis dilatata Pursh Fl. Amer. Sept. 2: 588. 1814
Synonyms: Habenaria dilatata (Pursh) Hooker Limnorchis dilatata (Pursh) Rydberg
Treatment appears in FNA Volume 26. Treatment on page 556. Mentioned on page 553, 557, 558, 559, 560, 561.

Plants 11–130 cm or more. Leaves few–several, ascending to recurved-spreading, scattered along stem, gradually reduced to bracts distally; blade linear, linear-lanceolate, oblong, or oblanceolate, 3.5–32 × 0.3–7 cm. Spikes very lax to very dense. Flowers resupinate, rather showy, conspicuous, white; lateral sepals spreading to reflexed; petals ovate- to linear-lance-falcate, margins entire; lip descending or apex adhering to dorsal sepal and petal apices, linear-lanceolate to lanceolate, without basal thickening, 4–11 × 2–5 mm, base slightly rounded-dilated to orbiculate, rarely rhombic, margins entire; rostellum lobes parallel to slightly divergent, directed downward, very small, obscure, rounded; pollinaria straight; pollinia remaining enclosed in anther sacs; ovary rather slender to stout, 5–15 mm. 2n = 42.


Varieties 3 (3 in the flora).

Selected References



1 Spur shorter than lip, clavate to slightly capitate. Platanthera dilatata var. albiflora
1 Spur nearly equaling to exceeding lip, slender to slightly clavate. > 2
2 Spur about equal to lip (mostly within 2 mm). Platanthera dilatata var. dilatata
2 Spur markedly exceeding lip (commonly 11/2 or more times length of lip). Platanthera dilatata var. leucostachys