Glandora diffusa, the purple gromwell, syn. Lithodora diffusa, Lithospermum diffusa, is a species of flowering plant in the family Boraginaceae. It is a mat-forming perennial growing to 15cm (06inches) tall by 60cm (20inches) or more wide, with dark green, hairy evergreen leaves and masses of blue or white 5-lobed flowers. It is suitable for cultivation in a rock garden or alpine garden.[1]
Although there is a variety with white flowers, G. diffusa var. alba,[2] the blue-flowered varieties are most valued in gardens for the intense azure color of their abundant blooms. A number of cultivars have been developed for garden use.[3]
Glandora diffusa is hardy down to -23C (USDA zones 6 - 8), and requires a position in full sun. It needs a well-drained acid or neutral soil, as it is susceptible to root rot. It requires vernalization to flower.[4]
The ancient Greek term lithodora literally means "stone gift", referring to its preferred habitat. Diffusa means "spreading", and refers to the plant's growth habit.[5]