Vascular Plants of North Carolina
Account for Whorled Mountain-mint - Pycnanthemum verticillatum   (Michaux) Persoon
Members of Lamiaceae:
Members of Pycnanthemum with account distribution info or public map:
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Section 6 » Order Lamiales » Family Lamiaceae
Author(Michaux) Persoon
DistributionPresent over most of the Mountains, and scattered over the northern Piedmont; apparently absent from the southeastern half of the Piedmont, and essentially all of the Coastal Plain. Note that P. torreyi was generally included within this species by most authors, and thus specimens between these two species might not have been examined recently for correct identification.

This is a Northern species, ranging from VT to IA, and then south to central NC and AR.
AbundanceUncommon to infrequent in the Mountains, and rare in the northern Piedmont, south to Northampton, Orange, and Iredell counties. Exact details of abundance are somewhat unsettled owing to confusion with P. torreyi.
HabitatThis is an upland species, generally found around rocky openings or outcrop margins, dry woodland borders, and other places in partial shade.
PhenologyBlooms from July to September, and fruits shortly after flowering.
IdentificationThis species is a typical mountain-mint, being about 3 feet tall, freely branched in the upper portions of the stem, and with numerous pairs of opposite leaves. The stem of this species is quite canescent (abundance of whitish hairs) on both the edges and the sides, a key identification character. In this species, the leaves tend to be lanceolate, narrower than many species in the genus, about 1.5-2 inches long and about 8-12 mm (2/5-inch) wide, about 4-5 times longer than wide, and nearly sessile, barely toothed along the margin. These species have rather flat-topped heads of about 1-2 inches wide at the ends of each branch, subtended by bracts, with the flowers being very small and generally white with some purple spots on the lower lip. There are many such heads in bloom over the plant, often dozens of them. This species is separated from the very similar P. torreyi by having the bracts of the inflorescence (and usually the leaves as well) canescent (whitened) on the upper surface, as opposed to glabrous or only very slightly pubescent in P. torreyi. Also, the latter species is limited to high pH soil, in case you can determine the soil chemistry (by other vegetation, for example). P. virginianum, also a high pH soil species, has more slender leaves (usually under 8-10 mm wide), and it does not have canescent stems, but is only somewhat hairy on the stem edges and occasionally the sides. This mountain-mint may take some time to find; look for a rather whitened stem and branches and lanceolate leaves to rule out most all other species.
Taxonomic CommentsNote that in RAB (1968) records for this species included P. torreyi, which has more recently been split out as a good species by Weakley (2018) and some other references.

Other Common Name(s)None
State RankS3
Global RankG5
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