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Herbaceous Perennial

Centaurea macrocephala
  • RHS Plants for pollinators

giant knapweed

A large, clump-forming perennial with simple or lobed leaves and yellow flower-heads 5cm across opening in summer from brown buds

Other common names
great-headed centaury
Synonyms
Grossheimia macrocephala

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Size
Ultimate height
1–1.5 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 Yellow 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
H7
Botanical details
Family
Asteraceae
Native to the UK
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

Correct

Plant range
Caucasus

How to grow

Cultivation

Best grown in moist but well-drained soil in sun or partial shade

Propagation

Propagate by seed sown in pots in a cold frame in spring or propagate by division in spring or autumn

Suggested planting locations and garden types
  • Coastal
  • Cottage and informal garden
  • Wildflower meadow
  • Wildlife gardens
  • Cut flowers
  • Flower borders and beds
Pruning

Deadhead regularly to prolong flowering

Pests

Generally pest-free

Diseases

May be affected by powdery mildews

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