Posted: 17/05/2013 at 09:41
What about a Chatham Island Forget - me - not (Myosotidium Hortensia).
Clump forming with robust dark green heart shaped leaves year round and dense sprays of tiny pale & dark blue flowers in summer. May need some winter protection but mine has done fine here in Cambridge pretty much left alone. I even managed to propagate some new plants last year from suckers forming on the mother plant.