Also known as Black Knapweed · Black Starthistle · Hardhead
Common Knapweed (Centaurea nigra) is a robust perennial with thistle-like purple flower heads, often found in meadows and disturbed ground. It's a hardy plant attracting
At-a-glance light, water, soil, and growing conditions from plant data
Full sun
100% intensity
Prefers at least 6 hours of direct sunlight per day for best flowering.
Moderate
50% intensity
Tolerates dry periods once established. Avoid waterlogging.
Well-drained
50% intensity
Moderate
50% intensity
Hardy in temperate climates. Tolerates a range of temperatures.
Low
25% intensity
Does not require much feeding; thrives in poor soil.
Safety information from plant toxicity data
| Attribute | Value |
|---|---|
| Toxic for humans | No 0/5 intensity |
| Toxic for pets | No 0/5 intensity |
| Edible | No |
None
Key traits and growing stats from plant data
Watering, pruning, propagation, and repotting details from plant data
Water regularly during establishment, especially in dry periods. Once established, Centaurea nigra is drought-tolerant and prefers well-drained soil. Avoid overwatering, which can lead to root rot.
Water deeply but infrequently, allowing the soil to dry out slightly between waterings.
Deadhead spent flower stalks to encourage repeat blooming and prevent self-seeding, especially if invasiveness is a concern.
Cut back the plant in late autumn or early spring to remove dead foliage and tidy its appearance. This also promotes vigorous new growth.
Common Knapweed can be propagated by seed sown in autumn or early spring, or by division of established clumps in spring. Seeds may benefit from a period of cold stratification.
Division is straightforward and helps rejuvenate older plants.
Repotting is generally not necessary for Centaurea nigra as it is typically grown in garden beds. If grown in containers, repot every 2-3 years in spring into a slightly larger pot with fresh, well-draining potting mix to prevent root-bound conditions.
Identify plants like this with ePlant AI
Snap a photo to get care tips and match similar species on the go.
Monthly activity intensity for bloom and fruit across both hemispheres.
Flowering & fruiting calendar
Flowering & fruiting calendar
Photos of Common Knapweed (Centaurea nigra)
Common names and botanical synonyms
Botanical classification
| Rank | Name |
|---|---|
| Kingdom | Plantae |
| Division | Tracheophyta |
| Class | Magnoliopsida |
| Order | Asterales |
| Family | Asteraceae |
| Genus | Centaurea |
| Species | Centaurea nigra |
Similar in genus Centaurea
Answers based on plant encyclopedia data
