Iridaceae
Iris

Iris japonica Thunb.

First published in Trans. Linn. Soc. London 2: 327 (1794)
This species is accepted
The native range of this species is China to Myanmar, Central & S. Japan. It is a rhizomatous geophyte and grows primarily in the temperate biome. It is used as a medicine.

Descriptions

Distribution
Biogeografic region: Andean. Colombian departments: Bogotá DC.
Ecology
Habitat according IUCN Habitats Classification: shrubland.
[UPFC]

Kew Species Profiles

General Description

Iris japonica is common in many parts of China and Japan and was introduced to Europe in 1792 from China by Thomas Evans of the East India Company. It was named in 1794 by Carl Peter Thunberg (1743-1828), a Swedish physician and botanist, who was a protégé of Linnaeus. Thunberg was employed by the Dutch East India Company and visited Japan from 1775-1778 (at a time when Japan was closed to most Europeans) and collected an impressive array of plants.

The great botanical artist Pierre-Joseph Redouté included a painting of this iris (known at that time as Iris fimbriata) in his Choix des plus belles Fleurs (1827-1833) (translation: 'Selection of the most beautiful flowers'), a fitting tribute to such a beautiful plant.

Species Profile
Geography and distribution

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.

Description

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.

Uses

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.

Cultivation

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.

This species at Kew

Iris japonica can be seen growing in the Duke's Garden.

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

Distribution
Japan
Ecology
Grassy and rocky slopes, open forest margins in hills and among rocks by streams.
Conservation
Not evaluated according to IUCN Red List criteria.
Hazards

All parts of both wild and cultivated Iris are poisonous, especially the rhizomes (swollen stems).

[KSP]

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation
Predicted extinction risk: not threatened. Confidence: confident
[AERP]

Uses

Use Medicines
Medical uses.
[UPFC]

Use
Ornamental, medicinal.
[KSP]

Common Names

English
Fringed iris

Sources

  • Angiosperm Extinction Risk Predictions v1

    • Angiosperm Threat Predictions
    • http://creativecommons.org/licenses/by/4.0

  • Herbarium Catalogue Specimens

    • 'The Herbarium Catalogue, Royal Botanic Gardens, Kew. Published on the Internet http://www.kew.org/herbcat [accessed on Day Month Year]'. Please enter the date on which you consulted the system.
    • Digital Image © Board of Trustees, RBG Kew http://creativecommons.org/licenses/by/3.0/

  • Kew Backbone Distributions

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0

  • Kew Names and Taxonomic Backbone

    • The International Plant Names Index and World Checklist of Vascular Plants 2025. Published on the Internet at http://www.ipni.org and https://powo.science.kew.org/
    • © Copyright 2023 International Plant Names Index and World Checklist of Vascular Plants. http://creativecommons.org/licenses/by/3.0

  • Kew Science Photographs

    • Copyright applied to individual images

  • Kew Species Profiles

    • Kew Species Profiles
    • http://creativecommons.org/licenses/by-nc-sa/3.0

  • Useful Plants and Fungi of Colombia

    • http://creativecommons.org/licenses/by-nc-sa/3.0