Imagine a “nice” Thistle, one with all the beauty and wildlife value but no prickly bits, that is knapweed.
Centaurea nigra is also known as Lesser Knapweed or Black Knapweed.. In fact it has quite a lot of different common names, too many to list here. It is a member of the Daisy family (Asteraceae) and that tells you tat it is not a single flower but a composite flower head made up of many little florets. Each of those little purple spikes is a complete flower and there are many of them.
This flower is a magnet for insects, especially Butterflies and it makes a great addition to a wildlife garden.