• 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 cyanus

bachelor's buttons

  • Other common names bachelor's buttons
    cornflower

    barbeau
    blaver
    blawort
    blue blaw
    blue bonnets
    bluebottle
    blue bow
    blue poppy
    blue sailors
    blue tops
    bluets
    break-your-spectacles
    brushes
    bunk
    corn binks
    cornbottle
    corn centaury
    French pink
    happy skies
    haw dods
    hurtsickle
    ragged robin
    ragged sailor
    witches' bells

    see more
  • 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 C. cyanus is an upright annual to 75cm, with simple or slightly lobed leaves and solitary deep blue flower-heads 3-4cm across in late spring and summer

  • Plant range N temp. regions

Characteristics

  • Foliage Deciduous

  • Habit Columnar/Upright

  • 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

Sunlight

  • Full Sun

  • Aspect South-facing or West-facing

  • Exposure Sheltered or Exposed

Soil

  • Sand

    Sand

  • Loam

    Loam

  • MoistureWell-drained

  • SoilSand, Loam

  • pHNeutral, Acid, Alkaline

Size

  • Ultimate height 0.5-1 metres

  • Ultimate spread 0.1-0.5 metres

  • Time to ultimate height 1-2 years

How to grow

Cultivation Grow in well-drained soil in full sun

Propagation Propagate by seed sown in-situ in spring

Suggested planting locations and garden types Flower borders and beds Cut Flowers Patio & Container Plants Coastal Wildflower meadow Wildlife Gardens

How to care

Pruning Deadhead regularly to prolong flowering

Pests Generally pest free

Diseases May be affected by powdery mildews

Advertise here

Did you find the information you were looking for?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now