Hardy perennial herbs, suitable for rock-garden cultivation during the summer. In winter they should be lifted into the cold frame or cool greenhouse.
Plant from October to April in a gritty soil containing plenty of leaf-mould. They like a sunny, well-drained position, and they should be given plenty of moisturo. Take cuttings in summer, or the plants can be divided in spring. Seeds may also be sown in mild heat in spring.
The flowers are mostly various shades of blue, while there are a few whito species. The flower in summer, and are borne on stems from 2-6 inches in height.