|Keys to Nature
|Key to the species of Platanthera (Orchidaceae) in the Chicago Region|
Key to the species of Platanthera (Orchidaceae) in the Chicago Region
William Alverson, Jennie Kuse
Adapted (by Jennie Kluse and Bil Alverson) from a key to the orchids of Wisconsin by Jeffrey R. Hapeman (www.botany.wisc.edu/orchids), Mike Homoya's Orchids of Indiana (1993, Indiana University Press), Fred Case's Orchids of the Western Great Lakes Region (1987, Cranbrook Institute of Science), and Charles J. Sheviak's key to Platanthera of North America (www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=125746).
1. Leaves all at base of stem - 2.
1. One or more leaves on stem, above base of stem - 4.
2. Single leaf near base of stem narrow at base and tongue-shaped at apex, at its broadest point much less than half of its length – Platanthera clavellata
2. Pair of leaves at base of stem very broad, their width more than half of their length – 3.
3. Stem with one to several bracts; upper sepals and petals spread away from each other; lip petal strap-shaped with blunt tip, and curving downwards and backwards - Platanthera orbiculata
3. Stem without bracts; upper sepals and petals overlap to form a "hood";
lip petal lance-shaped, tapering to a narrow tip, curved forward ("hooked" in appearance) - Platanthera hookeri
4. Lip petal fringed or deeply three-lobed - 5.
4. Lip petal not fringed or cut into deep lobes - 9.
5. Lip fringed but not lobed – 6.
5. Lip deeply three-lobed – 7.
6. Flowers orange - Platanthera ciliaris
6. Flowers white – Platanthera blephariglottis var. blephariglottis
6. Flower color intermediate - Platanthera x bicolor
7. Flowers purple – Platanthera psycodes
7. Flowers white or greenish-white – 8.
8. Flowers creamy white, fragrant; the three petals wedge-shaped with flat ends bearing fringes that cut 1/3 to 1/2-way down into each petal; spur much longer than the ovary - Platanthera leucophaea
8. Flowers green or greenish-white; the three petals very deeply cut into strap-like segments with some fringes that cut nearly down to the base of each petal; spur as long as or only slightly longer than the ovary - Platanthera lacera
9. Lip petal tapered to a slender tip – 10.
9. Lip petal blunt or slightly three-lobed, but not tapered to a slender tip - 11.
10. Flowers white, fragrant; base of lip usually abruptly broadened ("dilated") just above the base; spur typically longer than ovary; rare in our region - Platanthera dilatata var. dilatata
10. Flowers green, not fragrant; base of lip not abruptly broadened just above base; spur typically shorter than ovary - Platanthera huronensis
11. Stem with several conspicuous leaves; base of lip petal with a small tooth on each side and a short, nose-like projection (tubercle) in the middle of the upper surface - Platanthera flava var. herbiola
11. Stem with one full-sized leaf near base but above that the leaves smaller and bract-like; apex of lip petal with three rounded teeth; base of lip petal not lobed and not bearing a tubercle - Platanthera clavellata