Iris tenax

RHS Plant Profile
tough-leaved iris

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Synonyms

Iris gormanii

Herbaceous Perennial
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A strong, hardy rhizomatous evergreen perennial to around 40cm in height, with narrow, green, strap-like foliage. Blue-purple flowers, with central feathery white and yellow markings, appear in late spring

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Size

Time to Maturity
2–5 years

Growing Conditions

Chalk Clay Loam Sand
Moisture
Moist but well–drained or Well–drained
pH
Acid or Alkaline or Neutral

Position

Full sun Partial shade
Aspect
East–facing or 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)
H7

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Iridaceae
Native to GB/Ireland
No
Foliage
Evergreen
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
West N America, Mexico

How to Grow

Cultivation

Grow in any good garden soil that is moist but not waterlogged but prefers drier conditions. Dislikes root disturbance during growing season

Propagation

Propagate by division of rhizomes from midsummer to early autumn. See dividing irises

Suggested planting locations and garden types

  • City and courtyard gardens
  • Coastal
  • Cottage and informal garden
  • Gravel garden
  • Patio and container plants
  • Rock garden
  • Wildflower meadow
  • Flower borders and beds
  • Wall side borders

Pruning

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

Pests

May be susceptible to slugs, snails and thrips

Diseases

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