Centaurea 'Amethyst on Ice'

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knapweed 'Amethyst on Ice'

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knapweed 'Amethyst on Ice' RHS
knapweed 'Amethyst on Ice' RHS
Herbaceous Perennial
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A herbaceous perennial up to 40cm high with broadly lance-shaped green leaves and flowerheads with white ray florets and purple central discs from late spring to late summer; Centaurea flowers are attractive to bees

Position

Full sun, Partial shade

Soil Types

Chalk, Clay, Loam, Sand

Max Height

0.1-0.5 metres

Max Spread

0.5-1 metres

Size

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

Growing Conditions

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

Position

Full sun Partial shade
Aspect
West–facing or East–facing or South–facing or North–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
Asteraceae
Native to GB/Ireland
No
Foliage
Deciduous
Habit
Clump forming
Genus
Centaurea may be annuals, perennials or subshrubs, with simple or pinnately lobed leaves and showy thistle-like flowers-heads, often with enlarged outer florets
Name Status
Accepted

How to Grow

Cultivation

Grow in moist but well-drained soil in sun or partial shade

Propagation

Propagate by division in spring or autumn, or by root cuttings in winter

Suggested planting locations and garden types

  • Cottage and informal garden
  • Coastal
  • Prairie planting
  • Low Maintenance
  • Cut flowers
  • Flower borders and beds

Pruning

No pruning required, but deadheading may help to prolong flowering

Pests

Generally pest-free

Diseases

May be susceptible to powdery mildews but generally disease-free