When you prune clematis depends on the species. Without making it too confusing, you can break clematis into two groups — those that flower in spring and those that flower later, in summer and early autumn.
The spring flowering group will flower on stems produced the previous year and thus if you prune them late in the year, you will cut off next year’s flowers. Therefore, it is important that you prune these spring-flowering forms, just after they bloom so that they have a full season to produce growth for next year’s flowering.
These spring-flowering forms don’t need a heavy prune unless they have grown too big for their allotted space. Simply trim them to keep them in check and tidied up.
Summer-flowering forms, on the other hand, bloom on current year’s growth so pruning in early spring is good.
These can be pruned back as hard as you like to a node, which is where the leaf buds meet the stems, leaving as little as 50cm-6ocm from soil level if you wish.
You don’t have to prune them that hard but you can if you wish, leading to more vibrant blooms later in the year.
