Species in the genus Mentha:

Mentha x piperita / Koshouhakka コショウハッカ

Mentha x piperita, a 30-90cm tall perennial herb originating in Europe, used to be cultivated but escaped broadly to grow wild. Four-ridged stems are erect, with rhizomes well branching and extending sideways. The whole is glabrate and becomes significantly fragrant if rubbed. Leaves are opposite: oblong, with short petioles, crepe pattern, pointed tips, and margins with sharp serrations. Stem tips emerge 5-8cm long and 1.2-8cm wide raceme-like verticillasters; Flowers are bilabiate, cleft in four, and light purple. Bloom time: July-September.