Lithodora diffusa 'Grace Ward'

Lithodora diffusa 'Grace Ward' – Blue Gromwell

'Grace Ward' is a low, mat-forming evergreen grown for its star-shaped flowers in a gentian blue so saturated it reads as electric against the dark, bristly foliage. Flowering runs from mid spring into summer, with scattered repeats through autumn.

It needs sharp drainage and an acid to neutral soil, and dislikes lime, which makes it a natural companion to rhododendrons, camellias and other ericaceous plantings. The mat spreads to about half a metre, tumbling over a rockery edge, a retaining wall or the lip of a large container.

It is now classified as Glandora prostrata 'Grace Ward', the name accepted by the Royal Horticultural Society, which has given it an Award of Garden Merit.

• Mature height: 15 cm
• Mature width: 50 cm
• Light needs: Full sun to part shade
• Evergreen; needs acid to neutral soil