We've not a lot of information regarding the genus of thistle-like plants. From our experience they have good sized daisy-like flowerheads and are prickly in all their parts. Around 30 species, from western Europe, through to Iran and all the way north into Russia. One species in native to the UK, C. vulgaris, the Carline thistle.
The long-lasting flowerheads consist of numerous tiny flowers, each with nectar and pollen, although the lack of bright colours probably limits their attractiveness to insects. However, the seeds are much favoured by seed-eating finches.