Iris ensata Seeds | Japanese Water Iris
LATIN NAME: Iris ensata
COMMON NAME: Japanese Water Iris
Plant Profile
Japanese water iris is a clumping perennial of wet meadows and marsh edges in Japan, Korea, northeastern China and eastern Russia. It grows sixty to a hundred and twenty centimetres tall, with narrow, upright, ribbed leaves and large, flat, three-petalled flowers in early summer.
The wild flower is purple, but centuries of selection in Japan have produced white, pink, blue and patterned forms with flowers up to fifteen centimetres across. The falls carry a yellow signal, and the petals are often veined or edged in a contrasting colour. The leaves are stiff enough to stand through winter, and they turn yellow before dying back.
Science & Biotechnology
The species has one of the longest records of deliberate breeding of any iris, with named cultivars documented in Japan since the seventeenth century and thousands today. Research has looked at its tolerance of waterlogged, acidic soils and at the physiology of its flowering, which depends on a cold winter and a wet spring.
Its pigments, including the anthocyanins behind the deep purple forms, have been studied as natural colorants, and its chromosome behaviour has been examined because the cultivated forms show unusual fertility. Work on the genus has also used the species to understand how iris flowers are built for bee pollination.
Uses & Benefits
In Japan it is the subject of hanashobu gardens, planted in shallow water and viewed from a bridge or a boat in June. In the garden it is used at pond margins, in bog gardens and in damp borders, where the tall foliage gives structure after the flowers fade.
The flowers are excellent for cutting, and the stiff leaves are used in flower arranging. The rhizome has a place in Japanese and Chinese medicine, where it is dried and used as a bitter tonic, though the fresh root is irritant and not for home use.
In Japan the cut flowers are sold in bud, since a single stem carries several flowers that open in succession, and the foliage is used as a green in arrangements. The plants are also grown in large pots set in trays of water during the growing season, a method that suits small gardens.
Growing from Seed
Sow fresh seed in autumn, barely covered, and keep it wet and cold; germination is slow and uneven. Seedlings should stay in pots for two years.
Plant out in rich, acidic, moisture-retentive soil in full sun, with the rhizome just at the surface. Keep the ground wet through spring and early summer, then drier in winter, and divide clumps every three or four years after flowering. In a garden without a pond, the plant can be grown in a bottomless container sunk into the soil, with the rim just above the surface, so the root stays wet while the crown stays dry.
Our Take
Few plants give so much for a wet corner: a month of large flowers, a season of upright foliage, and almost no work once the clump is established.
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