Purple Gromwell Heavenly Blue A lovely plant for ground cover or the rock garden, Lithodora diffusa Heavenly Blue is an evergreen perennial with a prostrate, creeping, mat-forming habit. The small, hairy, grey-green leaves make a perfect foil for the intensely deep blue, star-shaped flowers, which are 12mm across and are borne from late spring to late summer. To encourage a dense, ground-covering habit, trim the current year’s growth by about half after flowering. Purple gromwell Heavenly Blue holds the RHS Award of Garden Merit. Site: Tolerates exposureSoil: Well drained, light, acid to neutral soilPosition: Full sun or partial shadeSeason of interest: Late spring to late summerHardiness: Fully hardyHeight: 15” (60cm) Spread: up to 18” (45cm)