This familiar and popular family has been well treated for the western Great Lakes region by Case (1987). This work should be consulted by anyone desiring more discussion than the very brief consideration presented here. The family includes some of our showiest wildflowers as well as some of our most inconspicuous and rare ones.
1. Lip a showy inflated pouch 1–5 cm long.
2. Plants with leafy stems; lip a closed pouch (i.e., open only at base above).
Cypripedium (in part)
2. Plants with leaves basal; lip split down middle above or open at base about half its length.
3. Basal leaf single, petiolate, the blade less than 7 cm long, produced in late summer and withering after the plant blooms the following spring; lip ca. 1.5–2 cm long, open about half its length basally above; plants less than 20 cm tall.
3. Basal leaves 2, longer, tapered to sheathing bases and not distinctly petiolate, present throughout the summer (but not winter); lip ca. 4–5 cm long, split down upper side; plants more than 20 cm tall.
1. Lip showy or inconspicuous, but not an inflated pouch with a small opening, usually ± flat with or without a slender basal spur (or if somewhat saccate, hardly showy and less than 1 cm long).
4. Flower solitary (rarely plants with 2 flowers in a population of 1-flowered ones).
5. Leaves 4–6, whorled; lip whitish or greenish yellow streaked with green or purple.
5. Leaf solitary or undeveloped at flowering time; lip light or deep pink.
6. Leaf linear, at most up to 7 (very rarely 10) mm wide, often poorly developed at flowering time, ± folded or plicate longitudinally, sheathing stem at base; plant from a small bulbous corm.
6. Leaf ± elliptic or lanceolate, usually over 7 mm wide and well developed at flowering time, flat, arising near middle of stem, sessile but not sheathing at base; plant from slender roots and rhizome.
4. Flowers 2 or more on one plant.
7. Lip produced into a distinct (usually slender and elongate) spur at base 2–40 mm long (pouch-like and only 2–3 mm in Coeloglossum).
8. Leaves cauline.
9. Spur a thick pouch 2–3 mm long, much shorter than the lip.
9. Spur slender, sometimes ± clavate, 7–40 mm long, ± equaling (at most slightly shorter than) to much longer than the lip.
Platanthera (in part)
8. Leaves all basal or nearly so, or absent at flowering time (bracts subtending flowers may be leaf-like).
10. Leaf solitary, absent or withered at flowering time, often dark-spotted above and purplish beneath; bracts absent or very minute at base of pedicels; perianth ca. 5–7 mm long (excluding the long spur), slightly asymmetrical.
10. Leaves 1–3, well developed at flowering time (if absent or withering, then perianth less than 5 mm long), green; bracts definite at base of pedicels; perianth of various sizes, bilaterally symmetrical.
11. Flowers entirely white and/or green, the lip lanceolate to narrowly linear, entire; lateral petals free.
Platanthera (in part)
11. Flowers with white lip (spotted or not) broadly ovate to oblong, often crenate or lobed; lateral petals connivent or fused with dorsal sepal to form a pink to purple hood.
12. Leaf 1; lip less than 1 cm long, spotted, notched at apex and with a lateral lobe on each side.
12. Leaves normally 2; lip over 1 cm long, unspotted, not lobed.
7. Lip at most somewhat swollen or saccate (but not with a spur 2 mm or more long).
13. Plants lacking green color (except sometimes in fruit), leafless with red, yellow, brown, or purplish stems arising from a coralloid rhizome.
13. Plants with green color, bearing leaves at some time in the year (if leaves absent at flowering time or plants apparently lacking green, arising from tubers, corms, or short rhizomes, not a coralloid mass).
14. Leaves a single opposite pair, definitely cauline, not at all sheathing the stem.
14. Leaves solitary, alternate, absent, or basal (or almost basal, with sheathing bases).
15. Stem leafy, with 4 or more conspicuous broadly ovate-lanceolate to elliptic leaves; perianth ca. 7–10 mm long; flowers greenish, at least the petals suffused with pink; upper part of stem and axis of inflorescence finely pubescent.
15. Stem with the leaves fewer than 4, narrow, and/or basal (or absent); perianth various, but if pinkish then 10 mm or more long and the vegetative parts completely glabrous.
16. Perianth 10–12 mm long, white or creamy, the flowers in a dense spike-like inflorescence.
Spiranthes (in part)
16. Perianth longer or shorter, or not whitish and the inflorescence not spike-like.
17. Perianth 10 mm or more long, at least in part usually with some shade of pink or purple (yellowish in a form of Aplectrum).
18. Flowers ca. 2–3 cm or more broad, the lip uppermost, bearded with a tuft of yellow-tipped hairs; leaf solitary (rarely 2), several times as long as broad.
18. Flowers less than 1.5 cm broad, the lip lowermost and not bearded; blade of leaf not over 3.5 times as long as broad.
19. Leaves cauline, sessile and clasping, very seldom over 1.5 cm long.
19. Leaves basal or absent at flowering time, sheathing at base or petioled, much larger (usually 7–15 cm long).
20. Leaf solitary, petioled, developing in fall and overwintering, usually withered before plant flowers.
20. Leaves 2, sheathing at base, developing in current season and present at flowering.
Liparis (in part)
17. Perianth less than 10 mm long, greenish, white, or yellowish, with no trace of pink or purple.
21. Leaves 1 or 2, sheathing at the base, the scape naked to the inflorescence; flowers on short pedicels, the raceme glabrous and not 1-sided nor noticeably twisted.
22. Leaf 1 (very rarely 2); perianth less than 4 mm long.
22. Leaves 2; perianth over 4 mm long.
Liparis (in part)
21. Leaves 3 or more (or withering at flowering time), the stem above them bearing small bracts or scales; flowers sessile or almost so in a narrow spike-like inflorescence, which is 1-sided or spirally twisted, or pubescent (or both).
23. Leaves ovate to elliptic, basal or nearly so, present and firm at flowering time, the midvein and/or other veins margined in white or pale green (not always visible in dry plants); lip pouched or saccate at the base.
23. Leaves ovate-elliptic to linear and grass-like, sometimes cauline, often withering at flowering time (in wider-leaved species), not marked with whitish; lip not pouched or saccate.
Spiranthes (in part)