There are several types of clematis. Some bloom on last years growth and these bloom in the spring. They should not be pruned until after they flower. You can prune these back as soon as they are done flowering. Summer and Fall bloomers should be pruned in early spring. You could leave them alone but they usually become a tangled mess and will benefit from some pruning. I like to prune the autumn clematis almost to the ground because otherwise it will tak...