Iris laevigata

RHS Plant Profile

smooth iris

Other common names

Japanese iris

Bogs Aquatic Herbaceous Perennial

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A rhizomatous perennial to 70cm in height, with erect, sword-shaped leaves and rich purple flowers 8-10cm in width, each fall with a narrow white flash at the base

Position

Full sun

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
pH: Acid or Neutral

Position

Full sun

Aspect: South–facing or West–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: Correct
Plant Range: Temperate Asia

How to Grow

Cultivation

Grow in moist to wet, deep, humus-rich, acid soil; thrives at the margins of ponds or streams. Tolerates some lime. See pond plants and bog gardens for further advice

Propagation

Propagate by division from mid-summer to early autumn

Suggested planting locations and garden types

City and courtyard gardens
Cottage and informal garden
Flower borders and beds

Pruning

No pruning required

Pests

May be susceptible to slugs, snails and iris sawfly

Diseases

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