Group 1 vines flower in spring, on growth from the previous year.
Prune these vines right after they finish blooming in spring. The new stems that grow will then have enough time to make flower buds for the following year.
How much to remove when pruning depends on the vine’s vigor and how large a support you’ve provided for it. Vigorous sorts, such as varieties of C. armandii, can be cut back almost to the ground. On the other hand, very little pruning is necessary for C. alpina and C. macropetala and other slow-growing varieties.
Older portions of the stems of some of these spring bloomers, such as C. montana, are often reluctant to resprout after being cut back, so avoid cutting these plants back into very old wood, keeping in mind that the plant will get somewhat larger each year. The best thing to remember is that, no matter how you prune Group 1 plants, the new shoots that appear after pruning are the ones that will bear flowers the following season. To some degree, the less you shorten stems when pruning, the earlier the blossoms will appear.