Vascular Plants of North Carolina
Account for Savanna Mountain-mint - Pycnanthemum flexuosum   (Walter) Britton, Sterns, & Poggenburg
Members of Lamiaceae:
Members of Pycnanthemum with account distribution info or public map:
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Section 6 » Order Lamiales » Family Lamiaceae
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Author(Walter) Britton, Sterns, & Poggenburg
DistributionOccurs essentially throughout the Coastal Plain, though may be locally absent in the far northeastern counties. Ranges west into the eastern edge of the Piedmont, west to Franklin, Chatham, Montgomery, and Anson counites. Disjunct to the southeastern Mountains, where known from three counties.

This is mainly a Coastal Plain species, ranging north to southeastern VA, and south to central FL and MS, with a few records for the mountains and Piedmont.
AbundanceCommon across nearly all of the Coastal Plain, including the Sandhills region. Very rare in the northeasternmost counties. Uncommon in the extreme eastern edge of the Piedmont, and rare and local in the Mountain portion of the range.
HabitatThis is widespread species of a great array of acidic soils of flat pinelands, especially characteristic of pine savannas and pine flatwoods. It also occurs in seepage pocosins, pocosin margins, powerline "savannas", ditches near pinelands, and other similar pinelands. However, in the mountains it is essentially limited to bogs.
PhenologyBlooms from June to September, and fruits from September to October.
IdentificationThis is a very well known species to biologists working Coastal Plain pinelands, being a medium to fairly tall herb reaching about 2.5 feet on average. It usually has several, ascending branches in the upper part of the plant, and the stem is covered in white hairs. The scattered pairs of opposite leaves are mostly lanceolate to elliptical, about 1.5 inches long but only about 2/5-inch wide, with a few teeth on the margin, a short petiole and a rounded leaf base. The leaves when broken, of this and all others in the genus, are extremely fragrant; this will not separate one Pycnanthemum from another, but a mystery plant in leaf in the Coastal Plain can often safely be called this species if the broken leaves have a minty smell. Each branch terminates in a dense head of very small white flowers, in a flat-topped cluster about 1-inch wide, but as there are so many such clusters in bloom at the same time, generally at the same level, the overall look is a white, flat-topped inflorescence often 5 inches or more across. The three lower petals form a lip that is spotted with purple. Thankfully, this species is different enough from the others in the genus as to not be confusing -- at least if it is growing in a pine-dominated habitat in the Coastal Plain. Farther west, in the Piedmont and mountains, recent splits have made identification of members of the genus very difficult, generally with calyx lobes the key (by using hand lens). Even so, Weakley (2018) mentions that a composite -- Eupatorium leucolepis -- can be confused with it when in vegetative condition, but the mountain-mint has square stems and very aromatic leaves.
Taxonomic CommentsNone

Other Common Name(s)Appalachian Mountain-mint is the commonly used name by gardeners. However, as it barely occurs in the mountains, and is essentially limited to the Coastal Plain savannas and flatwoods, Weakley (2018), Sorrie (2011), and the Digital Atlas of the Virginia Flora name it properly as Savanna Mountain-mint. This website thus strongly prefers to use the botanical common name and not the one used in the gardening trade.
State RankS5
Global RankG5
State StatusW6
US Status
USACE-agcpFACW link
USACE-empFACW link
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