Malaxis monophyllos (L.) Sw.
Habitat: Damp calcareous gravels, talus, peats, swales and fens. [Forested wetland]
Range: Alaska and British Columbia to Nova Scotia, south through northwestern New England to New Jersey, and west to Indiana and Minnesota, southward in mountains.
Aids to Identification: White adder's-mouth can be recognized by its single, basal, elliptical shining leaf, out of which rises the flower stalk bearing an unbranched cluster (raceme) of tiny, greenish-white flowers on short stalks. The plant stands 15-30 cm high, but, because of its coloring, easily blends into the surrounding forest floor. The flowers are 2-3 cm long, with spreading sepals and a lip which tapers to a sharp tip. M. monophyllos can be separated from the more common M. unifolia by its labellum (lower lip) that tapers to a point (the labellum of M. unifolia is two-lobed at the apex) and by having the flowers evenly distributed along the raceme, not crowded at the tip.
Ecological characteristics: Little is known about the ecology of this species. It appears to be rare through much of its range. Known Maine populations are not large. It may be overlooked, or there may be unknown characteristics of its cedar swamp habitat that restrict its distribution.
Phenology: An herbaceous perennial; in Maine flowering in July.
Synonyms: Represented in Maine not by the nominate variety but by the variety brachypoda (Gray) A. & D. Löve, a taxon formerly known as Malaxis brachypoda (Gray) Fern.
Known Distribution in Maine: This rare plant has been documented from a total of 20 town(s) in the following county(ies): Androscoggin, Aroostook, Franklin, Kennebec, Oxford, Piscataquis, Somerset, Washington, York.
Dates of documented observations are: 1871, 1874, 1878, 1893, 1895, 1896 (2), 1902 (2), 1904, 1915, 1916 (2), 1923, 1931, 1944, 1984, 1985, 1989 (2)
Reason(s) for rarity: Suitable habitat (calcareous or limy bogs) is scarce; appears to be local through much of its range.
Conservation considerations: The plant has been known to disappear from an area following logging. Like all orchids, it should not be collected or dug. It is not known to have been successfully propagated, and any plants offered for sale have almost certainly been dug from the wild.