Clematis pruning is determined by the flowering time, as they are classified into three groups:
Group 1 (Spring Flowering): This group includes early flowering clematis species, like Clematis montana. Prune these immediately after flowering in the spring. Only remove dead or weak stems asneeded.
Group 2 (Large-Flowered): These clematis bloom in early to mid-summer on the previous year’s growth. Prune them in late winter or early spring, around February or March. Remove any dead or damaged stems and cut back the remaining stems to a pair of healthy buds.
Group 3 (Late Flowering): This group includes clematis that bloom in late summer and autumn, such as Clematis viticella. Prune them hard in late winter or early spring, cutting all the stems back to a pair of strong buds, usually around 6 to 12 inches from the ground