Clematis x cartmanii 'Avalanche'

This valuable evergreen clematis, derived from two New Zealand species, has the largest flowers in this group. The 7.5cm (3in) pure white blooms, opening in March and April, can almost completely obscure the fresh green foliage and as a specimen in a large container it’s unbeatable. I’ve also seen it thriving on a sunny fence and tumbling over a low wall, but it appreciates shelter and good drainage. 1.8m (6ft)