Well suited for the rock garden or the mixed border in average soil. D. ruyschianum is one of the best of the perennials and is a handsome 18 in. high plant withof bright purple-blue. D. hemsleyanum is light blue with grey to about 1 ft. Among the D. Moldavica is lavender-blue with balm-scented . It is a favourite bee plant, growing to about 2 ft. All may be raised from and the perennials increased by division in spring. Watch out for slugs.