De Orchid. Eur., 20, 28, 36. 1817.
Herbs, perennial, terrestrial. Roots fleshy, fasciculate, slender to tuberous. Stems with foliaceous sheaths. Leaves basal or occasionally cauline. Inflorescences terminal spikes, flowers inserted in lax to dense, ± evident spiral, pubescent to glabrous, often glandular. Flowers resupinate, often somewhat apically recurved, white, cream, or yellow (pink in S. sinensis); perianth parts distinct or sepals basally connate, connivent; lip lanceolate to ovate or pandurate, rarely linear, fleshy to somewhat membranaceous, base with pair of calli, apex usually ± crisped; mentum or spur absent; column short, cylindric; anther cordate, apex acute or obtuse; pollinia clavate with slender viscidium; ovary sessile, cylindric.
North America, South America, Eurasia, Australia.
Species 45 (23 in the flora).
Two extra-limital species of Spiranthes have been reported from the flora. The Central American S. graminea Lindley was reported from southern Arizona (C. A. Luer 1975), based on plants subsequently described as S. delitescens Sheviak. The Asiatic S. sinensis Persoon was reported from Florida (J. Beckner 1996) based on plants of S. vernalis with unusual orange markings on the lips.
Catling, P. M. 1980b. Systematics of Spiranthes L. C. Richard in Northeastern North America. Ph.D. thesis. University of Toronto.
Catling, P. M. 1981. Taxonomy of autumn-flowering Spiranthes species of southern Nova Scotia. Canad. J. Bot. 59: 1253–1270.
Catling, P. M. 1982. Breeding systems of northeastern North American Spiranthes (Orchidaceae). Canad. J. Bot. 60: 3017–3039.
|1||Lip pandurate, subapical constriction deep, apex broadly dilated, glabrous adaxially; veins typically 3, lateral veins with branches wide-spreading toward margins; rachis glabrous or very sparsely pubescent.||Spiranthes romanzoffiana|
|1||Lip linear to lanceolate, ovate, oblong, or elliptic, at most only slightly constricted or scarcely to not at all differentiated from petals, glabrous to pubescent or papillate adaxially; veins various; rachis glabrous or densely pubescent.||> 2|
|2||Viscidium oval (2–2.5 times as long as wide); lip bright yellow or orange-yellow with greenish veins centrally; sepals and petals white; sepals basally connate.||Spiranthes lucida|
|2||Viscidium lanceolate to linear (3–12 times as long as wide), or absent; lip white or if yellowish or orange, sepals and petals creamy or ivory to yellowish, not pure white, or lip without greenish veins, or perianth green, or lip scarcely to not at all differentiated from petals; sepals basally connate to distinct throughout.||> 3|
|3||Rachis densely pubescent with all or many trichomes tapered, either pointed and not glandular or obscurely glandular; terminal glands equaling or narrower than stipes.||> 4|
|3||Rachis glabrous or densely pubescent with conspicuously glandular trichomes; terminal glands markedly broader than stipes, non-glandular trichomes of uniform thickness, blunt or truncate, not tapered or pointed.||> 5|
|4||Rachis with obscurely glandular trichomes, glands equaling or narrower than stipes; veins of lip divergent toward margin; southernmost Arizona.||Spiranthes delitescens|
|4||Rachis with all or many trichomes pointed, wholly not glandular; veins of lip straight, branches parallel; widespread, c, e flora.||Spiranthes vernalis|
|5||Lip with conspicuous, terminally widened, green (rarely cream-colored) diverging veins extending to near tip; lip glabrous on adaxial distal surface; leaves linear to linear-lanceolate.||Spiranthes praecox|
|5||Lip without conspicuously widened veins, veins sometimes greenish, either straight or divergent, not also widened; lip either pubescent or glabrous on adaxial distal surface; leaves linear to ovate.||> 6|
|6||Root solitary (rarely divided near tip), vertical, turbinate (4–12 mm wide, ratio of length/width about 5); rachis entirely glabrous; flowers gaping from near middle, tubular portion less than 3 mm; lip pure white.||Spiranthes tuberosa|
|6||Roots few to numerous, horizontal to strongly descending, slender to tuberously thickened, elongate (mostly 2–8 mm wide, rarely to 15 mm, ratio of length/width more than 5); rachis conspicuously or minutely and sparsely pubescent or glabrous; flowers gaping only from 2/3–3/4 their lengths from base, tubular portion more than 3 mm; lip white, creamy, yellow, or green in center, or often wholly green if undifferentiated from petals (i.e., flowers peloric).||> 7|
|7||Petals spatulate to obovate, suborbiculate, or ovate-elliptic, conspicuously shorter than sepals.||> 8|
|7||Petals slender, linear, linear-lanceolate, linear-oblong, slenderly elliptic, or linear-oblanceolate, slightly shorter to longer than sepals.||> 9|
|8||Lip with margins fleshy, ± inflexed at apex, apex acute; petals creamy white to greenish white; Nova Scotia.||Spiranthes casei|
|8||Lip truncate to broadly rounded at apex, apical margin thin, delicately crisped; petals whitish to yellow-green with longitudinal central green stripe; Texas.||Spiranthes parksii|
|9||Sepals basally connate for more than 0.4 mm; rachis glabrous or sparsely (rarely densely) pubescent.||> 10|
|9||Sepals not basally connate or connate for less than 0.3 mm; rachis sparsely to densely pubescent.||> 12|
|10||Lip broadest near middle, narrowed to base from between center and basal 1/3; perianth parts with basal 1/4 (or more) thick, fleshy, bright green, the remainder yellowish; lip variably orange centrally; sepals 4–6 mm; rachis glabrous, often farinose.||Spiranthes infernalis|
|10||Lip broadest near base, narrowed from below basal 1/4; perianth parts uniformly white to yellowish, membranaceous (except sometimes lip centrally fleshy, more deeply colored); sepals 4.6–15 mm; rachis glabrous or sparsely to densely pubescent, not farinose.||> 11|
|11||Rachis glabrous or sparsely pubescent, longest trichomes 0.18 mm, glands often sessile; lip lanceolate to lance-ovate, distal surface adaxially with dense cushion of peg-shaped trichomes; flowers creamy to markedly yellowish, slenderly tubular, apex of lip recurved less than to scarcely more than reflexed apices of sepals and petals.||Spiranthes porrifolia|
|11||Rachis sparsely (rarely densely) pubescent, longest trichomes 0.2–0.4 mm, glands obviously stalked; lip ovate to ovate-oblong, distal surface adaxially without dense cushion of peg-shaped trichomes; flowers white to ivory, strongly gaping with lip prominently diverging from sepals and petals.||Spiranthes diluvialis|
|12||Inflorescences with 5 or more flowers per cycle of spiral; spiral usually open and obvious.||> 13|
|12||Inflorescences with 3 or 4 flowers per cycle of spiral, spiral usually tight and obscure, then with 3 or 4 secondary vertical ranks evident.||> 21|
|13||Lateral sepals widely diverging from base, 8–10 mm; lip dilated at base, oblong toward apex, yellow centrally; flowers gaping from near middle; leaves fugaceous or persisting through anthesis; inflorescence secund to twisted usually no more than 180º; fall–winter blooming.||Spiranthes longilabris|
|13||Lateral sepals somewhat spreading to appressed, not widely diverging, 3.8–10 mm; lip ovate to oblong-quadrangular, basal dilation not distinct from oblong apex, white or creamy centrally; flowers gaping from near middle to merely apically; leaves persistent to fugaceous; spiral of inflorescence usually with few–several cycles of 360º, sometimes secund; spring–fall blooming.||> 14|
|14||Lip with distal margin laciniate-dentate; leaves usually linear with length/width ratio greater than 30 (rarely broader on stout, leafy plants nearly to more than 1 m), present at flowering.||Spiranthes laciniata|
|14||Lip with distal margin undulate to crisped, sometimes ragged, not laciniate-dentate; leaves lanceolate to ovate to obovate (linear in S. torta), with length/width ratio less than 30, often fugaceous and absent at flowering.||> 15|
|15||Flowers comparatively large, stout, perianth 5–12 mm, white to yellowish, lip often darker centrally, not green nor greenish yellow, ovary often equaling perianth in freshly opened flowers; leaves ascending, relatively slender, not ovate nor obovate, present at flowering; rachis conspicuously and densely glandularly capitate-pubescent.||> 16|
|15||Flowers comparatively small, slender, perianth usually less than 5.5 mm (if longer, lip green centrally and leaves ascending, slender, often fugaceous), ovary less than 1/2 length of perianth in freshly opened flowers; leaves strictly basal, spreading and ovate to obovate or oblanceolate, or ascending and slender, and often on base of stem in S. torta, often absent at flowering; rachis glabrous or sparsely to densely, minutely pubescent.||> 17|
|16||Lip distally truncate, 5–7.5 mm; flowers yellowish, cream, or ivory, arcuate-nodding for most or all length of perianth.||Spiranthes casei|
|16||Lip distally acute to rounded, not truncate, usually more than 7.5 mm (in shorter flowers ovary often much shorter than perianth); flowers white to yellowish, arcuate-nodding only at base of perianth.||Spiranthes cernua|
|17||Rachis densely pubescent; flowers cream to pale yellow, lip yellow centrally.||Spiranthes brevilabris|
|17||Rachis glabrous or sparsely and minutely pubescent; flowers yellowish to white, lip yellowish or green centrally.||> 18|
|18||Flowers creamy yellow to pale greenish yellow, lip yellow centrally.||Spiranthes floridana|
|18||Flowers white, lip green centrally.||> 19|
|19||Leaves ascending, linear, often absent at flowering; lateral sepals arching downward; s Florida.||Spiranthes torta|
|19||Leaves spreading, ovate to obovate, oblanceolate, or elliptic, present or absent at flowering; lateral sepals slightly spreading to appressed (not arching downward); various locales.||> 20|
|20||Leaves oblanceolate, withering at anthesis; sepals spatulate, green at base; spring-blooming.||Spiranthes eatonii|
|20||Leaves obovate, spreading, present or absent at anthesis; lateral sepals acuminate, white throughout; summer/fall-blooming.||Spiranthes lacera|
|21||Petals 6 mm; proximal portion of stem with recurved-spreading leaves.||Spiranthes ovalis|
|21||Petals 7.5 mm or longer; leaves wholly basal, or proximal portion of stem with ascending to recurved-spreading blades, or leaves absent at flowering.||> 22|
|22||Lip only slightly or not at all differentiated from petals (flowers peloric); often buds failing to open, setting seed agamospermically; column normal or abnormally formed or aborted; leaves usually absent at flowering.||Spiranthes cernua|
|22||Lip clearly differentiated from petals; buds opening into normal flowers; column normal; leaves present or absent at flowering.||> 23|
|23||Lip with variably evident median constriction, apical 1/3 of lip usually about 1/2 as wide as basal 1/3; veins of lip often with laterally diverging branches; flowers ascending.||Spiranthes diluvialis|
|23||Lip without conspicuous median constriction, apical 1/3 of lip 2/3 or more as wide as basal 1/3; veins of lip with branches parallel.||> 24|
|24||Basal calli relatively short and conic, as wide as high, mostly to 1 mm; lateral sepals distinct, spreading, often over top of flower; leaves absent at flowering (rarely persisting in Northern and High Plains, and New Mexico).||Spiranthes magnicamporum|
|24||Basal calli 1–2 mm; lateral sepals ± appressed, very rarely spreading over top of flower; leaves present at flowering (commonly absent in prairie populations).||> 25|
|25||Distal margin of lateral sepals obviously separated from adjacent margin of dorsal sepal, separation abrupt from base, commonly by about 1 mm; lip strongly curving from claw (resulting angle 20–60º), base cuneate; perianth creamy, yellowish, or greenish white.||Spiranthes ochroleuca|
|25||Distal margin of lateral sepals touching, or nearly touching, adjacent margin of dorsal sepal, or only gradually separated with distance from base; lip not strongly curving from claw (angle less than 30º), base cordate to truncate; perianth white to creamy or ivory, center of lip ivory to pale yellowish or rarely greenish.||> 26|
|26||Plants to 50 cm; leaves comparatively slender, ascending to spreading (flaccidly so because of membranaceous blades with thickened midrib); petioles of basal leaves less than 6 mm wide; leaves wholly basal or lower sheaths with ascending-spreading blades; perianth usually 8–11 mm; lip membranaceous to fleshy, less than 7 mm wide.||Spiranthes cernua|
|26||Plants to 100 cm or more; leaves broad, ascending to spreading (rigidly so because of aerenchymatous thickening of blade); petioles of basal leaves 7 mm or more wide; blades spreading-recurved on proximal cauline sheaths, frequently also on distal, leaves then extending to inflorescence; perianth (4–)10–18 mm (shorter in young or depauperate plants); lip fleshy, (4–)7–9.5 mm.||Spiranthes odorata|