Common Knapweed is a hardy perennial with raggedy, purple, thistle-like flowers. Its late flowering and seeding (June to September). It is a food source for many of the bees, flies, bugs and birds that visit the meadows in late summer. The Goldfinches especially flock together to feed on these seeds and can frequently be seen disappearing into the long sward.
This is sometimes seen growing on road verges and some old meadows. Best results are on really well drained acidic soil. This seeds late but will sometimes flower again if cut early before flowers are set.
It can easily be grown from seed sown at any time of year.