to 30cm or more across. The stems and tiny narrow, grey-green leaves are so closely packed that the plant feels hard to the touch. Flowers pearly-white, up to 1cm across, solitary and stemless, not freely produced on young plants. G.a. 'Caucasica' is a little smaller, and harder at maturity, regularly producing white flowers with pinkish veins. Flowering takes place in early summer. High mountains of Iran and the Caucasus on open slopes. Best in the alpine house or in a trough or scree outside, with protection from winter rainfall.