This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Mentha Cardiaca Gerarde; Baker, Journ. Bot. 2: 245. 1865.
Pubescent or glabrate, often much branched, 1 1/2°-2 1/2° high, the upper branches ascending. Leaves lanceolate to oblong-lanceolate or ovate-lanceolate, acuminate or acute at the apex, the lower 2'-3' long, the upper much smaller, all sharply serrate; flowers whorled in the upper axils; calyx-teeth subulate, about one-half as long as the tube.
Wet grounds, mostly along rivers and streams, Nova Scotia to New Jersey, Pennsylvania and District of Columbia. July-Sept.
Mentha arvensis L. Sp. Pl. 577. 1753.
Perennial by suckers, pubescent or glabrate; stems erect or ascending, simple or branched, 6-2° high, slender. Leaves oblong-lanceolate, oval or ovate, petioled, acute at the apex or the lower obtuse, crenate-serrate with bluntish teeth, rounded at the base, l'-2 1/2' long, 1/2'-1' wide, the upper not much smaller than the lower; whorls of flowers all axillary, usually about equalling the petioles; calyx pubescent, campanulate, its teeth triangular, about as long as the width of their base, acute or sometimes obtuse, one-third as long as the tube.
Perennial by suckers; stem more or less pubescent with spreading or scarcely reflexed hairs, or glabrate, erect, simple, or branched, usually slender, 6'-2 1/2° high. Leaves oblong or ovate-oblong, or oblong-lanceolate, slender-petioled, acute at the apex, or the lower obtuse, sharply serrate, narrowed to a somewhat cuneate acute or obtuse base, glabrous or very sparingly pubescent, the larger 2-3' long, 1/2'-1' wide; whorls of flowers all axillary, often shorter than the petioles; calyx oblong-campanulate, densely or sparingly pubescent all over, its teeth one-fourth to one-third as long as the tube.
In moist soil, New Brunswick to Manitoba, British Columbia, Virginia, Nebraska, New Mexico and Nevada. Consists of several races, differing in pubescence, leaf-form and size. Odor like Pennyroyal. July-Oct.
Mentha gentilis L. Sp. Pl. 577. 1753-Mentha sativa L. Sp. Pl. Ed. 2, 805. 1763.
Perennial by suckers; stem rather stout, ascending or erect, branched, glabrous or puberulent with short reflexed hairs, 1°-2° high. Leaves ovate or oval, short-petioled, sparingly pubescent with scattered hairs on both surfaces, often blotched, pinnately veined, acute at both ends, sharply serrate, the larger l 1/2'-2' long, the upper sometimes much smaller than the lower; whorls of flowers all axillary; pedicels glabrous; calyx cam-panulate, glabrous below, its teeth subulate, ciliate, one-half as long as the tube; corolla glabrous.
In waste places and along streams, Nova Scotia to northern New York, Iowa, North Carolina and Tennessee. Naturalized from Europe. Aug.-Oct.