Platanthera hookeri (Torrey) Lindley
Hooker's orchid
The specific epithet honors Sir William Jackson Hooker, an eminent early
nineteenth century English botanist.
DESCRIPTION: Plant glabrous,
arising from a cluster of fleshy, thickened roots, 10-60 cm tall (including
inflorescence). Leaves 2 (1 in young, sterile plants), opposite and
basal, broadly elliptical to suborbicular, 5-15 cm long and 5-12 cm wide,
keeled, dull and somewhat fleshy. Inflorescence a lax raceme, 6-30
flowered; flowers yellowish-green to green, each flower subtended by a lance-linear,
acuminate bract, stem of inflorescence bractless. Lateral sepals
lanceolate to oblong, 6-12 mm long and 2-4 mm wide, reflexed, colored as
flowers; dorsal sepal ovate to deltoid, 5-10 mm long and 3-6 mm wide,
connivent with petals over the column, colored as flowers. Petals
linear-lanceolate and falcate, 5-9 mm long and 1-2 mm wide, connivent with
the dorsal sepal over the column. Labellum triangular-lanceolate
and acute, 8-13 mm long and 2-5 mm wide, colored as flowers; base of labellum
with a clubbed nectar spur projecting behind, 12-25 mm long.
SIMILAR SPECIES: Although the two are only vegetatively similar, Platanthera
hookeri is often confused with P. orbiculata
(usually by those who have never seen P. hookeri). In bud or
flower, the two are easily separated: P. orbiculata
has bracts on the stem of the inflorescence, while the stem of P. hookeri
lacks bracts. Apart from that, the flowers are quite different, and flowering
specimens should never be confused.
HABITAT: In Wisconsin, Platanthera hookeri can be found in two
main habitat types. In the southern part of the state, it is found in moist,
rich deciduous woods, while in northern Wisconsin, it is found in sandy
Jack pine barrens.
FLOWERING DATES: June 1-July 1.
POLLINATION: Unknown. I have attempted to observe pollination of this
species with no success. Based on the color and morphology of the flowers,
I suspect that the pollinators are probably noctuid moths.
WI DISTRIBUTION: 
U.S. DISTRIBUTION:
Go directly to Wisconsin herbarium records.
Return
to the main LIST of the Orchids of Wisconsin.
Return to the main KEY to the Orchids of
Wisconsin.
