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Key to Spiranthes

Orchidaceae

Spiranthes

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1 Rachis of inflorescence with all hairs not glandular, tapering to a pointed tip; flowering Mar-Sep
1 Rachis of inflorescence either glabrous or with some or all hairs gland-tipped (capitate or clavate).
  2 Lip pandurate (fiddle-shaped), subapical constriction deep, apex broadly dilated; dorsal petals and lateral sepals forming a conspicuous connivent 'hood'; [NY, PA, OH, IN, and IL northwards]
  2 Lip sometimes constricted, but not pandurate; dorsal petals and lateral sepals not forming a connivent 'hood'; [collectively widespread]
    3 Viscidium ovoid; column white; lip bright yellow or orange-yellow, with greenish veins; sepals and petals pure white; flowering May-Jul
    3 Viscidium linear; column green; lip either white, or lip yellowish and lacking greenish veins; sepals and petals creamy, ivory, yellow, or greenish; collectively flowering Jan-Dec.
      4 Lip centrally green or white with green veins.
        5 Lip not papillate on the upper surface near the middle.
          6 Flowers 5-9 mm long, white, with green venation on adaxial surface of the lip only; primarily of pine flatwoods and savannas
          6 Flowers 8-17 mm long, creamy green, with green venation on the adaxial surface of all perianth segments; primarily of mixed hardwood-pine forests
        5 Lip papillate on the upper surface near the middle.
             7 Flowers fragrant; flowering late Oct-early Feb (-May); [of FL]
             7 Flowers not fragrant; flowering Feb-Sep; [collectively widespread in our area].
               8 Lateral sepals slightly downwardly falcate, oblique; [of FL]
               8 Lateral sepals held perpendicular to the stem, not oblique; [collectively widespread in our area].
                 9 Leaves oblanceolate, withering at anthesis; lateral sepals spatulate, green at base; flowering Feb-May
                 9 Leaves ovate to obovate or elliptic, spreading, present or absent at anthesis; lateral sepals acuminate, white throughout; flowering Jul-Sep.
                   10 Flowers densely arranged on the spike (ratio of spike length in mm: flower number < 2.3); plants glabrous or occasionally sparsely pubescent above; leaves usually absent at anthesis; flowering later, mostly Aug-Sep
                   10 Flowers laxly arranged on spike (ratio of spike length in mm: flower number ≥ 2.3); inflorescence capitate-pubescent; leaves usually persisting through anthesis; flowering earlier, mostly Jul
      4 Lip centrally yellow, cream, or entirely white.
                     11 Flowers < 4.5 mm long; rachis glabrous; flowers gaping from near middle, the tubular portion < 3 mm long; lip pure white; flowering Jun-Sep
                     11 Flowers > 5.0 mm long; rachis glabrous or pubescent; flowers gaping only from beyond the middle, the tubular portion > 3 mm long; lip white, creamy, or yellow.
                       12 Lip papillate on the upper surface near the middle.
                          13 Leaves basal, ovate.
                            14 Inflorescence densely pubescent
                            14 Inflorescence glabrous
                          13 Leaves upright, linear-lanceolate (or fugacious).
                              15 Callosities highly reduced, appearing as rounded mounds
                              15 Callosities not reduced, conical and upright.
                                16 Lip centrally white or very pale yellow; [of Interior Highlands of AR and OK and Coastal Plain of AR]
                                16 Lip centrally yellow (or greenish); [of FL]
                       12 Lip lacking papillae on the upper surface near the middle.
                                  17 Lateral sepals cupped (concave).
                                    18 Lip centrally white.
                                       19 Rostellum and viscidium absent; sepals 3.5-5 mm long
                                       19 Rostellum and viscidium present; sepals 4-6.1 mm long
                                    18 Lip centrally yellowish.
                                         20 Dorsal sepal and petals barely recurved; [of PA northwards]
                                         20 Dorsal sepal and petals recurved; [of Coastal Plain]
                                  17 Lateral sepals flat (not concave).
                                           21 Lip margin undulate.
                                             22 Flowers fragrant.
                                               23 Callosities reduced and mounded, 0.2-0.6 mm long; leaves usually absent at flowering
                                               23 Callosities pronounced, incurved or conical, 1-2.5 mm long; leaves present at flowering
                                             22 Flowers lacking fragrance.
                                                 24 Lateral sepals not oblique, held near the flower; flowering Aug-mid-Sep
                                                 24 Lateral sepals widely oblique; flowering Oct-Dec
                                           21 Lip margin crisped and lacerate.
                                                    25 Lateral sepals downwardly falcate, apices pointing toward the labellum apex
                                                    25 Lateral sepals sweeping upward, apices pointing toward dorsal sepal and petals.
                                                      26 Lip yellow on its lower surface; glands on the lower lip surface rounded.
                                                        27 Lateral sepals straight and typically curving apically over the petals; flowers typically nodding
                                                        27 Lateral sepals straight to somewhat falcate, not typically curving apically; flowers spreading or slightly ascending.
                                                          28 Lateral sepal apices bluntly acuminate, 7.7-10.2 mm long
                                                          28 Lateral sepal apices linear-lanceolate, (6-)10-11(-14) mm long
                                                      26 Lip white or very pale yellow on its lower surface; glands on the lower lip surface conical and reduced.
                                                            29 Lip centrally yellowish (sometimes faintly); lateral sepals linear-lanceolate; flowers frequently ascending; flowers occasionally peloric or cleistogamous; [north of the Ohio River]
                                                            29 Lip white; lateral sepals lanceolate; flowers frequently nodding; flowers rarely peloric or cleistogamous; [mostly south of the Ohio River]
                                                              30 Roots stoloniferous; leaves linear-lanceolate, 15-21.4 cm long × 1.4-1.7 cm wide; flowers fragrant (general 'floral' to vanilla-jasmine); [Long Island (NY) south to VA Eastern Shore]
                                                              30 Roots non-stoloniferous; leaves lanceolate, 8.7-20 cm long × 0.4-1.1 cm wide; flowers typically not fragrant; [widespread in our region]