A range of Saxifraga are on display in the Mountains House, including this one, S. sempervivum.
The genus Saxifraga comprises over 400 cushion-forming species from mountainous zones mainly of the northern hemisphere. This is a diverse genus, including annuals and perennials, which may be evergreen, semi-evergreen or deciduous, and whose star-shaped flowers are held in cymes, racemes or panicles and range in colour from white to pinks, yellows and oranges. S. sempervivum is variable in habit, producing arching racemes of pendent reddish purple flowers. This selection produces a tight cushion of silvery rosettes whose leaves are encrusted with calcium deposits which help protect the plant. It was recently discovered here in the Garden that these deposits contain vaterite, a rare calcium carbonate compound, which had only been found in small quantities in some crustaceans, birds eggs, salmon ears, meteorites and rocks. This observation is scientifically valuable because vaterite is produced synthetically to help control the release of drugs for therapeutic medicine, and this discovery will increase our understanding of the manufacture of synthetic vaterite for medicinal purposes.