Mentha × piperita (peppermint, "Koshohakka")

Japanese name: コショウハッカ （胡椒薄荷）
Scientific name: Mentha × piperita

[Overview]
A perennial 30–90 cm tall.
It spreads by rhizomes.
It is hairless, and the whole plant is often tinged with purple.
The whole plant also has a refreshing fragrance.
The stem is square in cross section.
Leaves are simple and opposite, lanceolate to lanceolate-ovate, 4–9 cm long and 1.5–4 cm wide.
The leaf margins are serrate.
Spike-like verticillasters 5–8 cm long and 1.2–1.8 cm wide are produced at the stem tips.
The flowers are two-lipped and 4-lobed, wisteria-pink.

[History]
It is a hybrid between Numa-hakka (Mentha aquatica / water mint) and Midori-hakka (M. spicata / spearmint).

[Uses]
It is often cultivated as a herb and used for herbal tea, potpourri, flavoring cooking, bath additives and so on.
The essential oil extracted from the leaves is used as a fragrance and for medicinal purposes.
It is also famous as the flavor of chewing gum and toothpaste.

[Cultivation]
Propagate by division or stem cuttings.
It prefers slightly moist, well-drained soil in sun to bright shade.
It is hardy and spreads by underground stems, so when planting in a garden, it is better to make a barrier underground to keep it from spreading too much.
For potted plants, water when the soil surface dries.
Fertilizer is not particularly necessary, and too much weakens the fragrance.
It is strongly drought tolerant and also tolerates heat and humidity, but if the branches become crowded, they become stuffy and disease may occur.

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