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Published In: Species Plantarum 2: 576. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 8/25/2017)
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17. Mentha L. (mint) (Tucker and Naczi, 2007)

Plants perennial herbs, with rhizomes. Stems erect or ascending, sometimes from a spreading base, sharply 4-angled, unbranched or branched, glabrous or hairy. Leaves sessile to long-petiolate, the petiole winged or unwinged, with various, strong, pleasant fragrances when crushed. Leaf blades variously shaped, unlobed, the margins toothed, the surfaces glabrous or hairy, also with usually conspicuous, sessile glands. Inflorescences ranging from small axillary clusters of mostly 8 to numerous flowers to terminal spikes or spikelike racemes, the individual flowers sessile (often in M. spicata) or short-stalked, with a pair of short, slender bractlets at the stalk base. Calyces actinomorphic or nearly so (sometimes slightly 2-lipped), lacking a lateral projection, symmetric at the base, cylindric to narrowly bell-shaped, the tube 10–13-nerved, glabrous in the mouth, the 5 lobes shorter than to longer than the tube, broadly to narrowly triangular, tapered to slender, sharply pointed tips, not spinescent, not becoming enlarged at fruiting, variously glabrous to hairy, usually also glandular. Corollas 2–7 mm long, nearly actinomorphic, not 2-lipped, the 4(5) lobes longer than the short, funnelform tube, the upper lobe (except in rare 5-lobed corollas) broader than the other 4 and often shallowly and broadly notched at the tip, white to lavender, pink, purple, or bluish purple, sometimes with darker spots or lines, the outer surface glabrous or hairy, sometimes also glandular. Stamens 4, long-exserted (sometimes nonfunctional and not exserted in hybrids or otherwise sterile plants), all similar in length, the filaments straight or slightly curved, the anthers small, the connective short, the pollen sacs 2, parallel, white or pink to dark bluish purple. Ovary deeply lobed, the style appearing nearly basal from a deep apical notch. Style long-exserted, equally 2-branched at the tip. Fruits dry schizocarps (rarely or not produced in hybrids or otherwise sterile plants), separating into 2–4 nutlets, these 0.5–1.3 mm long, broadly obovoid to broadly oblong-ellipsoid, more or less rounded at the tip, slightly and bluntly 3-sided to nearly circular in cross-section, the surface yellowish brown to reddish brown, dark brown, or black, with a network of fine, anastomosing ridges and pits, glabrous. About 18 species plus several widespread hybrids, nearly worldwide.

The genus Mentha has a long history of cultivation and a number of taxa are economically important as ornamentals and for their essential oils, which are used medicinally, as a fragrance, and as a flavorant. Hybridization and polyploidy are rampant (Harley and Brighton, 1977) and have been important in the formation of many of the commercially cultivated plants, most of which are propagated vegetatively by rhizome fragments. Taxa that are cultivated in the United States, but appear not to escape in Missouri, include M. pulegium L. (pennyroyal; see also the treatment of Hedeoma) and M. suaveolens Ehrh. (apple mint, pineapple mint). Because two of the hybrids are relatively frequently encountered in nature in Missouri, they are included in the key below. They are not given full species treatments, but are discussed under one of the parents.

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