When they bloom determines when to prune. Related articles: ``The Many Faces of Clematis. Get to know the wide variety of flower shapes and sizes this popular vine offers.'' ``Clematis with Everything. An avid collector uses shrubs an Garden Shrubs, Shade Garden, Garden Plants, Pruning Plants, Vegetable Garden, Clematis Trellis, Garden Trellis, Climbing Vines, Climbing Clematis