Iris japonica (fringed iris)

A native of Japan (except Hokkaido), where it is common in wooded hills, and westwards to Burma and Sichuan in China, it occurs from 500–800 m (2,400–3,400 m in southwestern China). It is widely cultivated, and it is possible that the high-elevation plants from southwestern China are naturalised rather than native.

Iris japonica is a perennial that spreads by creeping, above-ground rhizomes that root at intervals. The leaves are sword-shaped, evergreen and shiny green on one side but duller on the other. They are arranged in a broad fan and measure 30–80 cm long and 2.5–5.0 cm wide.

The flowering stems are erect, branched, 30–80 cm long with white, pale blue or purple flowers measuring 5 cm in diameter. The falls (three of the six perianth segments in Iris) have fringed margins and a yellow-orange crest. The flowers open in succession from March to May. The fruit is a capsule appearing from May-June.

Two popular cultivars include Iris japonica ‘Ledger’ that has white flowers with purple markings and an orange crest, and I. japonica ‘Variegata’ with creamy-white striped leaves.

Hand-coloured engraving of Iris japonica (as Iris chinensis) by an unknown artist in Curtis’s Botanical Magazine (1797).

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Iris japonica is widely cultivated as an ornamental, either as an outdoor plant (in sheltered areas) or in a cool greenhouse. It has received an Award of Garden Merit from the Royal Horticultural Society. In Chinese herbal medicine, the rhizome is used to treat injuries, and a decoction of the plant is used against bronchitis, rheumatism and internal injuries.

Iris japonica is easy to grow in warm temperate gardens or a cool greenhouse. Flowers can be susceptible to late spring frosts and will fail to flower after exceptionally cold winter weather.

Iris japonica can be seen growing in the Duke’s Garden and Temperate House.

Kew’s Economic Botany Collection contains samples of rhizomes of Iris japonica.

Search Kew's databases for more information on this species

Curtis’s Botanical Magazine (Wiley-Blackwell)

Flora of China – eFloras: Iris japonica

Royal Horticultural Society – Iris japonica