Vascular Plants of North Carolina
Account for Yellow Lady's-slipper - Cypripedium parviflorum   Salisbury
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Section 5 » Order Orchidales » Family Orchidaceae
AuthorSalisbury
DistributionPresent over all of the mountains; widely scattered across nearly all of the Piedmont, but seemingly absent in the extreme northeastern corner (no records east of Granville and Franklin counties). Absent in the Coastal Plain. Two varieties are present in the state, with var. pubescens occupying essentially the entire range above, but the nominate form -- var. parviflorum -- occurring only in the southern mountains (known from six counties).

This Northern species ranges south to central NC, central GA, and central MS, generally absent from the Coastal Plain south of DE.
AbundanceDeclining significantly in the state owing to poaching, deer browse, and presumably a few additional factors (discounting development -- a threat to nearly all species). Now uncommon to locally infrequent in the mountains. Rare to quite uncommon in the Piedmont, seemingly less rare in the north-central portions than in the western and southern portions. For example, the species was known from several dozen sites in Wake County around 1980, but only a few of these now survive -- the losses coming mainly to poaching, even in publicly owned areas. The nominate variety is quite rare, being tracked by the NC NHP as Significantly Rare and with a state rank of S1S2; the more widespread variety is not on any NHP list.
HabitatThe more numerous variety (var. pubescens) occurs mostly in rich hardwood forests, on lower or mid-slopes, or less so in bottomland forests. It is not really a taxon of high pH soils (i.e., not normally found in Basic Mesic Forests), but it does favor only very slightly acidic soils; it can often be found with Showy Orchis (Galearis spectabilis) and/or American Ginseng (Panax quinquefolius). On the other hand, the rare form (var. parviflorum) is limited to somewhat high pH soil, mainly over amphibolite rock in rich hardwood forests, often on upper slopes.
See also Habitat Account for Rich Wet-Mesic Hardwood Forests
PhenologyBoth forms bloom from April into June, and fruit in July and August. In the eastern Piedmont, it normally blooms only from late April to mid-May.
IdentificationWhen in bloom, this is one of the most spectacular wildflowers, particular in the Piedmont; even when in leaf, most biologists should be able to identify it, but the layman not likely so. The flowering stem normally grows to 1-2 feet tall and contains 3 to 6 quite large, widely elliptic and entire leaves that have deeply entrenched longitudinal veins; they average about 4 inches long. The large single flower sits atop the stem; it has the familiar bright yellow, large egg-shaped or sac-shaped lip that can be 1.5-2 long long. The two varieties are separated mainly by the sepals and lateral petals: the widespread variety has floral parts with only some purple blotching, and thus appearing mostly green, whereas the rare-in-NC var. parviflorum is so heavily blotched with purple that these parts look mostly or all purple.
Taxonomic CommentsOlder references, such as RAB (1968), named the species as Cypripedium calceolus, which is now restricted to the Old World; the form in NC was named as C. calceolus var. pubescens. As mentioned above, two varieties now occur in the state -- C. parviflorum var. pubescens and C. parviflorum var. parviflorum.

Other Common Name(s)Weakley (2018) gives Large Yellow Lady's-slipper as the common name for var. pubescens, and Small Yellow Lady's-slipper for var. parviflorum. The use of Moccasin-flower is poor, as Pink Lady's-slipper is more often used with that name.
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