This small, low-growing shrub makes an excellent container plant, as its star-like bright blue flowers keep on coming for weeks and weeks from late spring right through the summer months. Lithodora diffusa 'Heavenly Blue' is also a fine performer in the rockery with evergreen leaves providing ground cover all year. Also known as Purple Gromwell, it holds the RHS Award of Garden Merit and is easy to grow in sun or shade. Height: 15cm (6). Spread: 60cm (24).