Platanthera is a widespread genus containing an estimated 500 species. Species are often difficult to tell apart, and many crossbreed freely resulting many natural hybrids, thus complicating the taxonomy of the genus. It is in the Orchidaceae occurring across North America, Europe & Asia. Growth rises from a fleshy root system. The species in the genus Piperia have been merged into Platanthera by some taxonomists. However, the Jepson eFlora has not adopted this and continues to list ten California species as Piperia. They list differences between the two genera. Piperia has tubers that are more or less round, leaves present or not at flowering that are basal and not in a rosette. The inflorescence is a spike or a raceme. Platanthera has tuber-like rhizomes, alternate cauline leaves, and the inflorescence is generally a spike. Information about the California species in the genus Piperia can be found by clicking on the links for those pages.
Platanthera colemanii (Rand.Morgan & Glic.) R.M.Bateman see Piperia colemanii
Platanthera ciliaris (L.) Lindl. is a widespread species occurring throughout the eastern United States in pine flatwoods, seepage areas, and wet prairies. Photos by Alani Davis.
Platanthera cristata (Michx.) Lindl. is a widespread species occurring primarily on the coastal plain through out the eastern United States in pine flatwoods, seepage areas, and wet prairies. Photos by Alani Davis.
Platanthera dilatata (Pursh) Lindl. ex L.C.Beck, syn. Piperia dilatata, is native to the western United States. It is found growing in swamps, marshes and wet meadows. The flowers are white and fragrant. This species frequently hybridizes with other species blooming at the same time. Photo 1 by Dave Menke, photographer of the US Fish and Wildlife Service. Photo 2 by Walter Siegmund, from the Wikimedia Commons (see the source here).
Platanthera elegans Lindl. see Piperia elegans
Platanthera elongata (Rydb.) R.M.Bateman see Piperia elongata
Platanthera ephemerantha R.M.Bateman see Piperia candida
Platanthera michaelii (Greene) R.M.Bateman see Piperia michaelii
Platanthera nivea (Nutt.) Luer is a widespread species occurring primarily on the coastal plain throughout the eastern United States in pine flatwoods, seepage areas, and wet prairies. It is generally scarce, though locally abundant where it occurs. Recently it has been proposed that this species be moved to the genus Gymnadeniopsis along with several other members of the genus Platanthera. An interesting anecdote which I have heard repeated by many who have seen this flower is this is one of the whitest whites among flowers nearly glowing it is such a "bright" shade. Photos by Alani Davis.
Platanthera transversa (Suksd.) R.M.Bateman see Piperia transversa
Platanthera unalascensis (Spreng.) Kurtz see Piperia unalascensis
Platanthera yadonii (Rand.Morgan & Ackerman) R.M.Bateman see Piperia yadonii