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Herbaceous Perennial

Centaurea scabiosa
  • RHS Plants for pollinators

greater knapweed

C. scabiosa is an upright perennial to 75cm, with pinnately lobed leaves and reddish-purple flowers heads to 5cm across, usually with enlarged outer florets

Other common names
black top
Synonyms
Centaurea scabiosa var. petrophila

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Size
Ultimate height
0.5–1 metres
Time to ultimate height
2–5 years
Ultimate spread
0.1–0.5 metres
Growing conditions
Chalk
Clay
Loam
Sand
Moisture
Moist but well–drained
pH
Acid, Alkaline, Neutral
Colour & scent
StemFlowerFoliageFruit
Spring Green
Summer Purple Red Green
Autumn Green
Winter
Position
  • Full sun
  • Partial shade
Aspect

West–facing or South–facing or North–facing or East–facing

Exposure
Exposed or Sheltered
Hardiness
H6
Botanical details
Family
Asteraceae
Native to the UK
Yes
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

Correct

Plant range
Europe

How to grow

Cultivation

Prefers a well-drained fertile soil in a sunny position. Tolerant of dry, alkaline soils and established plants are tolerant of considerable neglect. Self-seeds readily and can become invasive

Propagation

Propagate by seed

Suggested planting locations and garden types
  • Wildlife gardens
  • Wildflower meadow
  • Low Maintenance
Pruning

No pruning required

Pests

Generally pest free. Resistant to browsing by deer

Diseases

May be affected by powdery mildews

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