Centaurea cyanus 'Black Ball'

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cornflower 'Black Ball'

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cornflower 'Black Ball' RHS

Synonyms

Centaurea 'Black Ball'

Plants for pollinators
Annual Biennial
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An upright annual to 75cm, with simple or slightly lobed leaves and solitary, very dark red flower-heads 3-4cm across in late spring and summer

Position

Full sun

Soil Types

Chalk, Loam, Sand

Max Height

0.5-1 metres

Max Spread

0.1-0.5 metres

Size

Time to Maturity
1–2 years
Max Spread
0.1-0.5 metres
Max Height
0.5-1 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 or West–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)
H6

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 well-drained soil in full sun

Propagation

Propagate by seed sown in-situ in spring or autumn

Suggested planting locations and garden types

  • Wildlife gardens
  • Wildflower meadow
  • Cottage and informal garden
  • Patio and container plants
  • Cut flowers
  • Flower borders and beds

Pruning

Deadhead regularly to prolong flowering

Pests

Generally pest-free

Diseases

May be susceptible to powdery mildews