type A - blooms on old wood in the spring
type B - can bloom on both old and new wood
type C - blooms on new wood later in the summer
Since our winters are so long, I do appreciate plants that can provide flowers in the spring. There are two type A species of clematis, C. alpina and C. macropetala that are suitable choices for Calgary gardens. In addition, these clematis are more shade tolerant than type B and C clematis. Since they bloom on old wood, they should not be pruned like most perennials. Instead, only remove any dead branches as required. A very low maintenance plant!
Here is a plant trials bulletin from The Royal Horticultural Society that provides details on the various cultivars of C. alpina and C. macropetala.
RHS Plant Trials Bulletin - C. alpina and C. macropetala