(Black knapweed; Hardheads). An English wildflower, this is a tough and hardy perennial that is loved by bees and butterflies. Clumps of slightly rough green leaves, and in summer upright, stiff stems carry bobble-like brown orbs which burst open at the top to reveal vibrant purply-pinkish flowers with feathery petals stretched outwards to 5cm across. Full sun to part shade, probably does best in average (not rich) soil and good drainage. 60-90cm H x 40cm W. 1 litre pot.