Knapweed
Centaurea nigra
Thistle-like purple heads on a tough meadow plant — it wants poor ground and resents being fed.
Light Happy in full sun, and untroubled by light shade.
Water Drought comes and goes without troubling it; no extra watering needed.
Height 60 cm
Spread 11.8 in
Spacing 30 cm
Spacing & sowing
- Plant spacing
- 11.8 in
- In-row spacing
- 11.8 in
- Between rows
- 15.7 in
- Square-foot density
- Not suited to SFG
Growing
- Type
- Flower · Perennial
- Botanical family
- Mixed / other
- Sunlight
- Happy in full sun, and untroubled by light shade.
- Watering
- Drought comes and goes without troubling it; no extra watering needed.
- Feeding
- Never feed it.
- Frost tolerant
- Yes
- Flowering
- June
- Pruning
- The only cut it needs is dead stems taken down in late winter.
- Overwintering
- Fully hardy; leave it to the winter.
Through the year
- Mar–Jun Bud Break
- Jun–Sep Flowering
- Sep–Nov Seed Set
- Nov–Dec Dormancy
- Jan–Mar Dormancy
Pests & problems
- Powdery mildew Powdery mildew through dry summers — seldom serious, though better air circulation helps if it persists
- Knapweed gall fly larvae (Urophora), which do the plant no harm and point to a healthy patch of ground
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com