Description from
Flora of China
Mentha ×piperita Linnaeus var. citrata (Ehrhart) Briquet.
Herbs perennial, bearing leafy stolons, glabrous or subglabrous throughout. Petiole of middle stem leaves ca. 2 mm; leaf blade broadly ovate to elliptic, 2-4 × 1.5-3 cm, base rounded to shallow cordate, margin remotely serrate, apex obtuse; upper leaves reduced, sometimes sublanceolate, apex acute. Verticillasters in terminal spikes 2.5-4 cm; bracts linear-lanceolate, shorter than verticillasters. Pedicel ca. 1 mm. Calyx tubular, ca. 1.5 mm, glandular; teeth linear-subulate, ca. 0.5 mm. Corolla purplish, ca. 4 mm, tube ca. 2.5 mm. Fl. Jul-Aug.
Cultivated in China.
Perhaps best regarded as a cultivar of Mentha ×piperita.
Beijing Shi, Hangzhou Shi, Nanjing Shi, and other cities [Europe]