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.

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.

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.

June 1-July 1.

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.

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