Centaurea scabiosa var. petrophila
greater knapweed
An upright perennial to about 1.5m, with branched stems and greyish-green, broadly lance-shaped leaves to 25cm long, and reddish-purple flowers heads to 5cm across, usually with enlarged outer florets, from mid to late summer
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Size
Ultimate height
1–1.5 metresTime to ultimate height
2–5 yearsUltimate spread
0.5–1 metresGrowing conditions
Moisture
Well–drainedpH
Acid, Alkaline, NeutralColour & scent
Stem | Flower | Foliage | Fruit | |
Spring | Green | |||
---|---|---|---|---|
Summer | Red Purple | Green | ||
Autumn | Green | |||
Winter |
Position
- Full sun
Aspect
West–facing or South–facing or East–facing
Exposure
Exposed or Sheltered Hardiness
H6Botanical details
- Family
- Asteraceae
- Native to GB / Ireland
- 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 well-drained soil in a sunny position. Especially tolerant of dry alkaline soils
Propagation
Propagate by seed in spring, or propagate by division in spring or autumn
Suggested planting locations and garden types
- Wildlife gardens
- Wildflower meadow
- Cottage and informal garden
- Flower borders and beds
Pruning
Self-seeds readily so prune after flowering if seed is not required
Pests
Generally pest-free
Diseases
May be susceptible to Powdery mildews
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