“In the hardest and sheerest limestones of the far Southern and Eastern ranges [of the Alps] it chooses the most adamantine precipices for its home, and there alights in only the most microscopic crannies of an apparently unbroken cliff-face. Here its rootstock, yellow and fat, flows out and in and far until it has precisely moulded the cranny as if old wax had been poured in and hardened.”
Reginald Farrer, writing of Physoplexis comosa (Phyteuma comosum) in The English Rock Garden. He goes on about it for pages, in euphuistic ecstasy.
The plant is now protected in the wild, and so habitat-collected seed is contraband, but enough rock gardeners grow it that seed is occasionally available through the seedlists offered by the rock garden societies. The seed, fine as dust, is fairly easy to germinate if sown directly; this plant sowed itself in a trough.
It is said to be the favorite food of slugs. I wouldn’t know about that.