Ceratostigma

The hardy plumbago. Around 8 species, Himalayas to China & eastern Africa. Simple, alternate leaves, shrubby or herbaceous, with very blue flowers, late in the year and often good autumn colour. Found in pretty dry areas in the wild, but seems relatively happy in border. Spreads gently. Generally cut back to the ground by frosts.

Nectar tucked away deep in a long flower tube means that only a few pollinators can gain access. It is one of those flowers that seems to be visited more by butterflies and day-flying moths such as hummingbird hawk-moth, than bees and flies.