Common knapweed

Common Knapweed

©Philip Precey

Common knapweed

Scientific name: Centaurea nigra
The tightly packed, thistle-like purple flower heads of common knapweed bloom on all kinds of grasslands. Also regularly called 'black knapweed, this plant attracts clouds of butterflies.

Species information


Height: up to 1m

Conservation status


When to see

June to September


Common knapweed, also known as 'black knapweed', is a thistle-like plant that can be found on all kinds of grasslands, from roadside verges to woodland rides, clifftops to lawns. It is in bloom from June to September and is a huge favourite of all kinds of butterflies, including common blues, marbled whites and meadow browns, and is sometimes covered in these species.

How to identify

The bright pink-purple 'flowers' of common kanpweed are actually composite flower heads made up of many small 'florets' (tiny flowers), surrounded by a crown of long, ragged, pink bracts (leaf-like structures). It has deeply divided, oblong leaves.



Did you know?

Due to its hardy and fast spreading nature, common knapweed is considered an invasive weed in North America.

How people can help

Our gardens are a vital resource for wildlife, providing corridors of green space between open countryside, allowing species to move about. In fact, the UK's gardens provide more space for nature than all the National Nature Reserves put together. So why not try planting native plants and trees to entice birds, mammals and invertebrates into your backyard?