Orchid Family (Orchidaceae)

Hundreds of species of orchids are native to natural habitats of North America. A few of the more prominent species are described below.

Species of lady-slipper orchids grow on the surface of the ground, in open forest, prairie, and wetlands such as bogs and fens. Lady-slipper orchids have one or several large, showy flowers. The lip is greatly inflated (this is the "lady's slipper"), with the margins of its orifice inrolled. A nectar-seeking, pollinating insect, usually a bee, passes through this orifice into the chamber of the lip, and is then drawn to the vicinity of the stigmatic surface by nectar, odor, and a visual trail of dots known as nectar guides. If the insect is carrying a pollinium from another lady-slipper flower, it is deposited to the receptive stigmatic surface, and then another pollinium is picked up, commonly on the forehead of the bee, which then exits through another hole. Worldwide, there are about 50 species of lady-slipper orchids. The stemless lady-slipper (Cypripedium acaule) is a widespread species in North America, with solitary flowers that are a lovely pink and sometimes white. The yellow lady-slipper (C. calceolus) occurs in calcium-rich, moist forest and wetlands and has a solitary, bright-yellow flower. The showy lady-slipper (C. reginae) is relatively tall, reaching 16 in (40 cm) in height, and has one to three large, pink-and-white flowers. The white lady-slipper (C. candidum) occurs in calcium-rich wetlands and prairie and has a single white flower.

There are about 50 species of orchids in the genus Orchis. These plants have large, showy flowers that are white or white-and-pink in color. North American species include the showy orchis (Orchis spectabilis), which occurs in rich woods in eastern North America, while the round-leaved orchis (O. rotundifolia) occurs in the west.

There are about 450 species of Platanthera orchids. These orchids have their relatively small, but quite beautiful flowers arranged in a spiral fashion along an erect stalk. Some wide-ranging, white-flowered species in North America include the small woodland orchis (Platanthera clavellata) and the tall white orchis (P. dilatata). The yellow fringeless orchis (P. integra) has yellow flowers. The long-bracted orchis (P. viridis) and pale-green orchis (P. flava) have greenish flowers. The crested orchis (P. cristata) has orange flowers, and the purple fringed orchis (P. psycodes) has purple flowers.

The grass-pink orchid (Calopogon pulchellus) is a pink-flowered species that occurs widely in acidic wetlands, especially bogs. The dragon's-mouth or arethusa Showy lady-slipper (Cypripedium reginae). Photograph by Robert J. Huffman. Field Mark Publications. Reproduced by permission. (Arethusa bulbosa) produces a single pink flower, and is also a species of acidic wetlands. The rose pogonia or snake-mouth (Pogonia ophioglossoides) also develops a single pink flower, as does the calypso or fairy-slipper (Calypso bulbosa).

Ladies' tresses develop their relatively small but lovely flowers in a spiral arrangement along an erect stem. Most species have white or white-yellow flowers. Some widespread examples include the nodding ladies' tresses (Spiranthes cernua) and slender ladies' tresses (S. gracilis).

Coral-roots are saprophytic orchids of forests. These plants lack chlorophyll and depend on nutrition available from the decomposer food web of the forest floor to supply their needs. These plants and their flowers are reddish purple in color. The most widespread species is the spotted coral-root (Corallorhiza maculata).

The helleborine (Epipactus helleborine) is a species native to Eurasia that has become widely naturalized in North America. This green-flowered orchid is a common weed in many cities.