Iris ensata 'Royal Banner'

RHS Plant Profile

Japanese water iris 'Royal Banner'

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Bogs Herbaceous Perennial

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A clump-forming perennial to 90cm in flower, with erect, strap-like green leaves to 60cm bearing large single, blue-purple blooms with yellow centres, in summer

Position

Full sun, Partial shade

Soil Types

Clay, Loam

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

Moisture: Poorly–drained or Moist but well–drained
pH: Acid or Neutral

Position

Full sun Partial shade

Aspect: South–facing or West–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: Not established

How to Grow

Cultivation

Grow in moist to wet, deep, humus-rich, acid soil, plant rhizomes 7.5cm deep; it thrives at the margins of ponds or streams, but avoid winter waterlogging

Propagation

Propagate by division of rhizomes after flowering from midsummer to early autumn every three years

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Wildlife gardens
Cut flowers

Pruning

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

Pests

May be susceptible to slugs, snails, iris thrip and iris sawfly

Diseases

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