Keep your clematis down to size, looking good and flowering with proper pruning.
Prune early blooming clematis like alpine, Montana, and downy clematis after flowering. Pruning at any other time removes the flower buds that form on the plants in summer prior to spring bloom. Remove only the older and weak stems to the ground and reduce the overall size as needed.
Some clematis like Bee’s Jubilee, Nelly Moser, and Henry produce flowers on last year’s growth and a second flush of flowers on the current season’s growth. Remove all weak and dead stems on these in late winter or early spring. Reduce the height of overly long stems by pruning these back to a set of healthy buds.
Late flowering varieties like Jackman, Italian, golden, and sweet autumn clematis flower only on the current season’s growth. Prune these back to one or two feet above the ground in late winter or early spring as needed.
A bit more information: All clematis are divided into the groups described above. You will often read pruning guidelines for clematis listed in one of these groups. Group 1 includes the Clematis that bloom on old growth. Group 2 includes Nelly Moser and others that bloom on old and new growth and Group 3 are those that bloom on the current season’s growth.