Japanese iris Iris ensata
Japanese iris (Iris ensata) is a deciduous perennial flowering plant in the Iridaceae family, native to Japan, eastern Russia and northeast China. It grows 60 cm–1.1 m (24 in–3.6 ft) tall and 40–60 cm (16–24 in) wide, wants full sun and high water, and is hardy to about -30 °C (-22 °F). Space plants about 45 cm (18 in) apart.
Plan Japanese iris in your garden →
Free. Draw your beds, then watch it grow through the year in 2D and 3D.
Japanese iris at a glance
| Type | Perennial flowering plant, deciduous |
|---|---|
| Family | Iridaceae |
| Mature height | 60 cm–1.1 m (24 in–3.6 ft) |
| Mature spread | 40–60 cm (16–24 in) |
| Spacing | 45 cm (18 in) centre to centre |
| Sun | Full sun, at least 6 h of direct sun a day |
| Water | High; drought tolerance none, waterlogging tolerance high |
| Soil pH | 5–6.5 |
| Cold hardiness | About -30 °C (-22 °F) once established (roughly USDA zone 4) |
| Heat stress | Likely above about 30 °C (86 °F) |
| Flowering | from about June for 2–4 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Low |
| Pollinator value | Moderate |
| Edible | Not grown as food |
| Native to | Japan, eastern Russia and northeast China |
| Common in gardens of | 🇯🇵 Japan |
Is Japanese iris toxic?
- People: mildly toxic
- Cats: moderately toxic
- Dogs: moderately toxic
- Parts: rhizomes, leaves
Rhizomes contain irritant glycosides (iridin) that cause drooling, vomiting and diarrhoea.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Japanese iris
No well-documented helpful pairing. Group it with plants that like full sun and high water.
See Japanese iris in a botanical garden
It grows in these sample gardens, which you can walk through in 3D:
- The Huntington (18 plants)
- Brooklyn Botanic Garden (10 plants)
- China National Botanical Garden (8 plants)
- The Butchart Gardens (6 plants)
- Fairy Lake Botanical Garden (8 plants)
- Missouri Botanical Garden (12 plants)
- Monet’s gardens at Giverny (40 plants)
- Denver Botanic Gardens (8 plants)
- Jardin botanique de Montréal (10 plants)
Questions about Japanese iris
- How far apart should I plant Japanese iris?
- About 45 cm (18 in) apart, centre to centre. A mature plant spreads 40–60 cm (16–24 in).
- Does Japanese iris need full sun?
- Full sun: at least 6 hours of direct sun a day.
- How much water does Japanese iris need?
- High water. Drought tolerance is none and waterlogging tolerance high.
- How cold-hardy is Japanese iris?
- It tolerates about -30 °C (-22 °F) once established, roughly USDA zone 4.
- When does Japanese iris flower?
- From about June for 2–4 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Japanese iris poisonous to cats and dogs?
- For cats it is moderately toxic; for dogs moderately toxic; for people mildly toxic. Rhizomes contain irritant glycosides (iridin) that cause drooling, vomiting and diarrhoea.
- What grows well with Japanese iris?
- There is no well-documented companion pairing for Japanese iris. Group it with plants that like the same sun (full sun) and water (high).
Sources and evidence
Evidence grade B (B: extension service or peer-reviewed).
- RHS Plant Finder, Royal Horticultural Society
- Missouri Botanical Garden Plant Finder, Missouri Botanical Garden
- ASPCA Toxic and Non-Toxic Plant List, ASPCA
Notes and assumptions
- Typical garden-form values; cultivars and local conditions differ.
- Needs moist, acidic soil in the growing season but dislikes standing water in winter; intolerant of lime.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Bearded iris Iris germanica
- Siberian iris Iris sibirica
- Dutch crocus Crocus vernus
- Gladiolus Gladiolus x hortulanus
- Freesia Freesia refracta hybrids
- Montbretia (crocosmia) Crocosmia x crocosmiiflora
- African iris Dietes grandiflora
- Bugle lily (watsonia) Watsonia borbonica