Dierama 'Cosmos'

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A slow-growing evergreen perennial, to 1.2m high in flower, with fine clumps of narrow, grass-like leaves. From mid to late summer, produces slender, arching stems bearing a succession of pendent, bell-shaped dark purple flowers with contrasting silvery bracts

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

1-1.5 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
2–5 years
Max Spread
0.1-0.5 metres
Max Height
1-1.5 metres

Growing Conditions

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

Position

Full sun
Aspect
South–facing
Exposure
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)
H4

Colour & Scent

Season Stem Flower Foliage Fruit
Spring
Summer
Autumn
Winter

Botanical Details

Family
Iridaceae
Native to GB/Ireland
No
Foliage
Semi evergreen
Habit
Tufted, Clump forming
Genus
Dierama are evergreen, clump-forming cormous perennials with long, narrow leaves and slender arching stems bearing nodding, bell-shaped flowers in summer
Name Status
Accepted

How to Grow

Cultivation

Grow in humus-rich, well drained soil in an open, sunny spot; these plants like moisture during the growing season but dislike winter wet. Add a compost mulch in spring. May benefit from winter protection in colder areas. See dierama cultivation for more detailed advice

Propagation

Propagate by division of mature clumps, carefully separating corms in spring. Young plants and divisions can be slow to establish

Suggested planting locations and garden types

  • City and courtyard gardens
  • Coastal
  • Cottage and informal garden
  • Prairie planting
  • Gravel garden
  • Flower borders and beds

Pruning

Tidy any winter-damaged foliage by cutting to the base in spring

Pests

Generally pest-free

Diseases

Generally disease-free