Andrew Chick Ecology

Common Knapweed (Centaurea nigra) is one of the characteristic wildflowers of British grasslands, flowering from mid-summer well into autumn. Its deep purple flower heads are a familiar sight along roadside verges, woodland rides, field margins and in meadows, particularly where the ground has escaped intensive agricultural improvement.

For insects, Common Knapweed is an exceptionally valuable plant. Its flower heads produce plentiful nectar and pollen, attracting a remarkable variety of visitors. Butterflies are particularly fond of it, including Meadow Brown, Gatekeeper, Ringlet, Marbled White, Common Blue, Peacock, Red Admiral and several skippers. On a warm summer’s day, a good patch of flowering knapweed can be one of the best places to look for butterflies.

It is equally important for bees and hoverflies. Bumblebees, including Common Carder Bee, Red-tailed Bumblebee and White-tailed Bumblebee, regularly visit the flowers, alongside solitary bees and numerous species of hoverfly. Beetles and other small insects also feed on the flower heads or take advantage of the abundance of prey attracted to them.

Knapweed supports insects in other ways too. The foliage and flower heads provide food for the larvae of a number of moths and other invertebrates, while its seeds are eaten by several insects and, later in the year, by birds such as Goldfinches.

Perhaps the best indication of its wildlife value is simply to stop beside a flowering patch on a sunny July or August day. What initially appears to be just another purple flower can be alive with bees, butterflies, hoverflies and beetles. For that reason, Common Knapweed is one of the most valuable plants to retain in meadows, verges and other areas managed for wildlife.