Iris ensata 'Summer Storm'

RHS Plant Profile
Japanese water iris 'Summer Storm'

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Herbaceous Perennial
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A vigorous herbaceous perennial with narrow, pale green foliage and stems to 90cm in height. The buds are almost black, opening up to three deep purple flowers with yellow centres around 18cm across from late spring to early summer

Position

Full shade, Partial shade

Soil Types

Clay, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
0.5-1 metres

Growing Conditions

Clay Loam Sand
Moisture
Poorly–drained
pH
Acid

Position

Full shade Partial shade
Aspect
West–facing or South–facing or East–facing
Exposure
Exposed or Sheltered
Hardiness

Hardiness Ratings

All ratings refer to the UK growing conditions unless otherwise stated. Minimum temperature ranges (in degrees C) are shown in brackets

  • H1A: under glass all year (>15C)
  • H1B: can be grown outside in the summer (10 - 15)
  • H1C: can be grown outside in the summer (5 - 10)
  • H2: tolerant of low temperatures, but not surviving being frozen (1 to 5)
  • H3: hardy in coastal and relatively mild parts of the UK (-5 to 1)
  • H4: hardy through most of the UK (-10 to -5)
  • H5: hardy in most places throughout the UK even in severe winters (-15 to -10)
  • H6: hardy in all of UK and northern Europe (-20 to -15)
  • H7: hardy in the severest European continental climates (< -20)
H6

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Iridaceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Clump forming
Potentially harmful
Harmful 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
Genus
Iris may be rhizomatous or bulbous perennials, with narrow leaves and erect stems bearing flowers with 3 large spreading or pendent fall petals, alternating with 3 erect, often smaller, standard petals, in late winter, spring or early summer
Name Status
Accepted

How to Grow

Cultivation

Grow in moist to wet, deep, humus-rich, acid soil; it thrives at the margins of ponds or streams

Propagation

Propagate by division of rhizomes from midsummer to early autumn

Suggested planting locations and garden types

  • City and courtyard gardens
  • Coastal
  • Cottage and informal garden
  • Wall side borders
  • Flower borders and beds

Pruning

Remove any dying foliage in autumn, old flower stems can be cut down after flowering

Pests

May be susceptible to slugs and snails

Diseases

May be susceptible to aphid-borne viruses, bacterial soft rot and grey moulds; see Iris diseases