Lithodora diffusa 'Heavenly Blue' (Zahn's gromwell) is a member of the Boraginaceae family. This perennial exhibits a bushy growth habit and is characterized by its evergreen foliage. It has a hardiness rating of hardy – average winter (-10 to -5ºc) and is hardy through most of the UK apart from inland valleys, at altitude and central / northerly locations. May suffer foliage damage and stem dieback in harsh winters in cold gardens. Plants in pots are more vulnerable.
When fully mature, Lithodora diffusa 'Heavenly Blue' can reach an ultimate height of 0.1–0.5 metres and a spread of 0.1–0.5 metres. For optimal growth, it prefers west–facing or south–facing aspect and exposed positions. It thrives best in chalk or loam or sand soil types and should be placed in full sun.
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