Mentha ×piperita L.

Rhizomatous perennial; stems glabrous or sparsely hairy, to 60 cm or more tall, often submerged; aerial stems erect, often purple. Lvs very variable, petiolate; lamina 1–6 × 1–3.5 cm, lanceolate-elliptic, elliptic, oblong-ovate, ovate, or suborbicular, aerial lvs somewhat rugose, serrate, hairy or glabrous; base cuneate to rounded; apex sharply acute. Infl. of a terminal, ± rounded head and 1–3 distinct verticels of shortly pedicellate fls below, or an oblong spike, sometimes with 1–4 distinct verticels below, often glabrous except for calyx teeth. Calyx 3–4 mm long, tubular, purple, dotted with oil glands; teeth equal, ciliate, narrow-acuminate, much < tube at anthesis. Corolla 5–6 mm long, mauve or lilac, glabrous; tube exserted. Stamens small, included. Nutlets not formed.

[From: Webb et al. (1988) Flora of New Zealand. Volume 4.]

Flowering: Jan.–May.