Black knapweed looks like a thistle but has no prickles; it is closely related to thistles hence the familiarity. That close knit purple flower head is smaller than the more expansive flower of its close cousin, the greater knapweed.
The seed case under the flower head turns hard and black once the petals have died away and that is where its other name, hardhead, comes from.
A very common plant across Dorset.
|Common Name||Common Knapweed|
|Alternative Name(s)||Black Knapweed|
|Scientific Name||Centaurea nigra|
|Species Group||Daisy Family Compositae|
|Family||Daisy family - Compositae|
|Flower Colour Group||Purple|
|Look for||Thistle-like flower but without thorns or prickles|
|Additional Identification Notes|