Stems 3-8 dm, with recurved hairs; lvs broadly ovate, 3-7 cm, commonly more than half as wide, toothed, rounded or even subcordate at base; fls numerous in 1-3 verticils closely aggregated to form a globose or ovoid to rarely short-cylindric spike; accessory heads on peduncles 2-10 mm may develop from the upper axils; cal and pedicels hairy; 2n=96. Native of Eurasia, found as an escape here and there in our range. A hybrid with no. 8 [Mentha longifolia (L.) L.] is M. ؤumetorum Schult.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.