About
Iris ensata, the Japanese water iris, is a herbaceous perennial to 80 cm forming a dense clump of erect, strap-shaped foliage. In midsummer, rich violet-purple flowers to 12 cm across appear with broad, rounded falls each bearing a small white or yellow midrib. A classic moisture-loving iris for a bog garden, pond margin or deep, moist border.
About the genus
Iris, the irises, are rhizomatous or bulbous perennials producing narrow, often sword-shaped leaves and distinctive flowers with three large, spreading or pendent fall petals alternating with three erect standard petals. They flower from late winter to early summer in every colour of the rainbow.
Growing conditions
SunlightFull shade, Partial shade
Soil typeClay, Loam
Soil pHAcid
Soil moisturePoorly-drained
AspectSouth-facing, East-facing, West-facing
ExposureExposed, Sheltered
UK hardinessH6
Plant details
Plant typeHerbaceous Perennial
HabitClump forming
FoliageDeciduous
Height0.5-1 metres
Spread0.1-0.5 metres
Time to full height2-5 years
Suggested usesCity and courtyard gardens, Coastal, Cottage and informal garden
Native toE Asia
ToxicityHarmful if eaten. Wear gloves and other protective equipment when handling. Pets: Harmful if eaten. For further information and contact numbers regarding pets, see the HTA guide to potentially harmful plants
Care notes
CultivationGrow in moist to wet, deep, humus-rich, acid soil; it thrives at the margins of ponds or streams
PruningRemove any dying foliage in autumn, old flower stems can be cut down after flowering
PropagationPropagate by division of rhizomes from midsummer to early autumn
Pest resistanceMay be susceptible to slugs, snails and thrips
Disease resistanceMay be susceptible to aphid-borne viruses, bacterial soft rot and grey moulds; see Iris diseases