Phyteuma nigrum

A purple pretty thing for a border, trough or rock garden.

Black Horned Rampion. Native of open spots in woods in Central Europe. For any rich, well drained soil in full sun or partial shade. Excellent in the rock garden. It has a basal rosette of narrow heart-shaped green leaves and deep spiky-looking, but soft, purple cone-shaped flowers on long stems in summer. 30cm H.

I photographed it flowering, but now cannot find it. Here is the sort of thing, but mine seems to be a little more compact and a longer inflorescence.

Ozelotenor, CC BY-SA 3.0 , via Wikimedia Commons