Kentucky Plant Atlas




Taxonomic distinction unclear    No county information
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Lamiaceae <Nepetoideae-Menthinae> Mentha "longifolia" {spicata x longifolia, or pubescent spicata}
Mentha longifolia auct. non (L.) Huds.
ALI: EU HAB: H-9?, ::?, E?, 5 ABU: n/a, n/a, 4
Although the name longifolia has been applied to plants known as "horse-mint" in North America, almost all of these plants are now considered by Tucker & Naczi (2007) to be a pubescent variant of spicata or the hybrid between spicata and longifolia (= X villoso-nervata Opiz, sometimes called "American Spearmint"). There may also be confusion with the hybrid of lanceolata and suaveolens (= X rotundifolia). In Ky. there are only old or obscure records of longifolia, from FAYE, JESS, KENT and MEAD during ca. 1930-1950 (M), and these all need to be checked. True longifolia is a diploid (2n = 24) that is close to the tetraploid species, spicata (2n = 48). Based on Tucker & Naczi (2007), it can be distinguished by its hairs all uniseriate (versus occasionally dendroid on abaxial leaf surface), its leaves widest near the middle (versus near base), and its fertile anthers 0.28-0.38 mm long (versus 0.38-0.52 mm).