Vascular Plants of North Carolina
Account for Large Round-leaved Orchid - Platanthera orbiculata   (Pursh) Lindley
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Members of Platanthera with account distribution info or public map:
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Section 5 » Order Orchidales » Family Orchidaceae
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Author(Pursh) Lindley
DistributionOccurs in the northern Mountains, south to Madison County. Also found sparingly in the northwestern Piedmont (Stokes County), presumably in the Sauratown Mountains.

This Northern orchid has a very broad east-west range, occurring all across southern Canada from the Atlantic to the Pacific, and south to PA, northern IL, and WA. South of PA it is limited essentially just to the Appalachian Mountains, south to NC and eastern TN.
AbundanceUncommon south to Watauga County, but rare farther south and in the northwestern Piedmont. Though recorded from just nine NC counties, it is not named as a Watch List species by the NC NHP, and biologists should be able to find the species on their own by enough walking through its habitats.
HabitatThis is a species of upland/montane hardwood and mixed forests, and is not at all found in damp or wet ground like most other NC Platanthera species. Weakley (2018) noted that it is found "especially over amphibolite", a rock yielding high pH soils. However, many locales are probably on acidic soils.
PhenologyFlowers from June to September, and fruits shortly after blooming.
IdentificationThis species is probably better known for its vegetative characters than for its flowers. It is unique for a Platanthera in the state in having two very large and rounded basal leaves that lie flat (or nearly flat) on the ground. Each leaf is about 4-5 inches long and nearly as wide. Several other orchids, in other genera (Liparis, Galearis), do have large basal leaves that lie flat or nearly flat on the ground, but they are not nearly as large as these. The flowering stem is mostly leafless and is about 1-1.5 feet tall. The final 4-5 inches contain the flower cluster, consisting of about 15-20 fairly large flowers, but each is a pale green or whitish-green that does not stand out at a distance. (The lip tends to be whitish and the petals are pale green.) This is one of the few species of Platanthera in the state that is not truly rare and is likely the easiest one to find in the mountains (though only in the northern counties).
Taxonomic CommentsNone, other than being placed in the genus Habenaria through much of the last century.

Other Common Name(s)Dinner-plate Orchid, Lesser Round-leaved Orchid, Round-leaved Orchid
State RankS3
Global RankG5
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US Status
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B.A. SorrieSame data. July 2020. Photo_non_NCPhoto_non_NC
B.A. SorrieGlacier NP, MT, in mixed forest. Photo_non_NCPhoto_non_NC
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