Menyanthes trifoliata (bogbean, "Mitsugashiwa")

Japanese name: ミツガシワ （三槲、三柏）
Scientific name: Menyanthes trifoliata

[Overview]
A perennial 20–40 cm tall, found mainly in wetlands and ponds of the alpine zone, often growing in colonies.
Thick underground stems creep long distances through the soil.
The leaves are basal and trifoliate, and the leaflets are elliptical, 4–8 cm long, and thick.
The leaf margin has blunt teeth or is entire.
The leaves have long petioles whose bases form sheaths.
It produces racemes; the flowers are about 1–1.5 cm across and white to pale purple, and the corolla is 5-lobed with dense white hairs on the inside.
There are two types of flowers: long-styled flowers (with a long pistil and short stamens) and short-styled flowers (with a short pistil and long stamens); the type differs from plant to plant, and only the long-styled flowers set fruit.
The fruit is a spherical capsule about 0.5 cm across.

[History]
It is a plant of such ancient origin that fossil seeds have been found in strata of the Oligocene (about 34 million to 23 million years ago), and some plants found in lowlands are survivors of the glacial period (relict plants).

[Uses]
The leaves are called suisaiyo and are used medicinally.

[Cultivation]
Propagate by division.
It prefers a sunny site.
Paddy soil is suitable for planting.
The aboveground parts die back in winter, but keep the water from drying up throughout the year.
For potted plants, sink the whole pot in water and keep the base of the plant always submerged.
From spring to autumn, bury slow-release chemical fertilizer or fermented oil cake in the soil.

[Notes]
The Japanese name likens the shape of the leaflets to kashiwa leaves, or to the family crest (kamon) "Mitsu-gashiwa."

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