The Stemmacantha we sell are now known as Rhaponticum.
The dense flowerheads with many tiny flowers produce nectar and pollen that is used by bumblebees, honeybees, butterflies and moths, hoverflies, beetles and a whole lot more. At the end of flowering, the seeds may be taken by goldfinches, linnets and other seed-eating birds. Unlike many relatives such as knapweeds, it seems able to defend itself against herbivorous insect attack as it produces an insect moulting hormone that disrupts the development of would-be herbivores.