• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Centaurea 'Amethyst on Ice'

knapweed 'Amethyst on Ice'

  • Other common names knapweed 'Amethyst on Ice'

  • Family Asteraceae

  • 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

  • Details 'Amethyst on Ice' is 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

Characteristics

  • Foliage Deciduous

  • Habit Clump-forming

  • 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

Sunlight

  • Full Sun

  • Partial Shade

  • Aspect South-facing or West-facing or East-facing or North-facing

  • Exposure Sheltered or Exposed

Soil

  • Loam

    Loam

  • Chalk

    Chalk

  • Sand

    Sand

  • Clay

    Clay

  • MoistureMoist but well-drained

  • SoilLoam, Chalk, Sand, Clay

  • pHNeutral, Acid, Alkaline

Size

  • Ultimate height 0.1-0.5 metres

  • Ultimate spread 0.5-1 metres

  • Time to ultimate height 2-5 years

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 Flower borders and beds Cut Flowers Low Maintenance Prairie Planting Coastal Cottage & Informal Garden

How to care

Pruning No pruning required, but deadheading may help to prolong flowering

Pests Generally pest-free

Diseases Generally disease-free but may be affected by powdery mildews

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