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Herbaceous Perennial

Centaurea nigra
  • RHS Plants for pollinators

common knapweed

An upright, branching perennial to 75cm, with simple or pinnately lobed leaves and thistle-like purple flowerheads to 4cm across, with conspicuous blackish involucres

Other common names
bell weed
black centaury
see moreblack knapweed
bowl weed
bull weed
button weed
churl's head
club weed
crop weed
hard weed
hardhead
hardheads
horse knops
horse knots
iron hard
iron heads
iron weed
knob weed
knot weed
lesser knapweed
loggerheads
nob weed
Spanish buttons
sweeps
tassel
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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

South–facing or North–facing or West–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
NW to C Europe

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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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