How do I prune my Clematis? Group 1, 2, 3s or A, B, Cs
Clematis fall into three basic 'pruning groups'. The 'prune groups' are a separate classification of clematis in the 'family' groups (such as 'the Montana group') which take into account the parentage of the specific cultivar or the 'type' groups (such as 'the Evergreens') which take into account some specific attribute of the plants. There is, however, a connection between 'family' or 'type' groups and pruning groups, as almost all members of a specific family group or type group would fall into the same prune group. For more information on Clematis types and groups, please see the FAQ titled 'Clematis types'.
These pruning suggestions are for established vines that have been in the ground for at least three years. Young vines should all be pruned to 12 inches the second spring and to 18 inches the third spring. It helps to develop more shoots, a fuller vine, and a better root system.
Group 1 - Certain species clematis and their cultivars which bloom early in the year. Some of the more commonly found representatives of this group include the Montanas, which are extremely vigourous in USDA zones 5 and warmer. Other clematis in Group 1, which are becoming more commonly available, are varieties of C. alpina and C. macropetala. These clematis will also develop into very large specimen plants over time. Another example in Group 1 is C. armandii and its cultivars. All of the Group 1 clematis bloom on growth made the previous year. They can be pruned to keep them within their alotted space, or to remove dead and unsightly foliage. Note however, if they are pruned late in the season, or before they flower in the year, you will be cutting off potential flower buds. They should be pruned right after flowering, if at all.
Group 2 - These are the large flowered hybrids. They are often divided again into two subgroups - 2a and 2b. The main difference between the two subgroups is: those in 2a normally bloom in the spring and possibly again in the fall; those in 2b bloom mainly in the spring then intermittently all through the summer. Subgroup 2b types usually continue to grow as well as bloom as the season progresses so in the spring you might have a mass of blooms at waist height and by autumn they may be blooming overhead. The flowers of both subgroups tend to be smaller later in the season and might be more intensely or differently colored as well. All of the clematis in Group 2 bloom on 'old wood' (actually on short shoots from old wood) and should not be pruned except for deadwood pruning in early spring after the leaf buds open slightly. Note that those in subgroup 2b also bloom on new wood (see information below about alternate pruning for special puposes). The number of later flowers can be increased if the seed heads from the first flowering are removed right after the blooms drop their tepals.
Group 3 - These are the summer blooming varieties such as the viticellas, Jackmanii types, texensis, the...