Acorus calamus (calamus, "Shobu")

Japanese name: ショウブ （菖蒲）
Scientific name: Acorus calamus

[Overview]
An emergent aquatic perennial 50–120 cm tall, growing in colonies in ponds, reservoirs, wetlands and similar places.
The whole plant has a distinctive strong fragrance.
White rhizomes 10–20 mm in diameter creep horizontally, branch often, and send out many roots from the nodes.
Leaves are alternate in two ranks and erect, sword-shaped and linear, 50–120 cm long and 1–2.5 cm wide, with a raised midrib.
The leaf base is tinged pale pink and clasps the stem and the inner leaves.
From among the leaves, a cylindrical spadix 4–8 cm long and 6–10 mm in diameter emerges at a slant, and the bract is 20–40 cm long and 5–8 mm wide.
The bract resembles the leaves in shape and size and emerges in the same direction as the flower stalk, so the inflorescence appears to come from the center of the leaves.
The flowers are densely set on the spadix, about 5 mm in diameter, each with six pale yellowish-green tepals.
Fruit is rarely seen; it is a red, oblong berry.

[History]
It appears in the Man'yoshu under the name 'ayamegusa'.
It was also called 'ayame'.
The shape of its leaves was likened to a sword, and its name also echoes 'shobu' (martial spirit) and 'shobu' (contest), so it was considered an auspicious plant in warrior society.

[Uses]
Its fragrance is believed to ward off evil, so on Tango no Sekku (the Boys' Festival) a bath is prepared with the rhizomes and leaves, and they are also tucked into the eaves as a charm against evil.
The dried rhizome is used as a crude drug.
The dried leaves are said to repel insects.

[Cultivation]
Propagate by division or from seed.
Division is possible all year round but is best done before spring growth begins.
For seed, sow in a wet place so that the seeds do not dry out.
It suits sunny, wet sites with soil rich in organic matter.

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