Clematis is a type of flowering vine. Generally, there are three varieties of clematis, determined by when the plants flower. The first of the varieties is called group A or group one and flowers the earliest. The second is group B or group two and flowers both early in the season and later in the season. The final general variety is group C or group three and flowers last. When the varieties of clematis flower also determines when they need to be pruned.
Group A varieties of clematis produce flowers on the previous year's growth. This type of clematis includes the species Clematis alpina and Clematis macropetala. The flowers produced by group A varieties usually appear in the spring, while the buds of those flowers develop the summer before. Group A varieties typically feature small flowers between 1 and 3 inches (2.54 to 7.62 cm) in diameter. This type doesn't do as well in cold climates, as the flower buds need to survive freezing winters.
The second group, or group B, starts blooming in the spring on old growth and continues to bloom on new growth. There are two subsections of group B. One section blooms on two separate occasions while the the other section produces flowers continuously from spring into late summer. Common varieties of clematis in group B include Lincoln star and Ramona.
Group C flowers in the late summer. The blooms form on growth from the current season. Examples of species in this group include Clematis integrifolia and Clematis viticella. Group C also include hybrids that produce larger flowers. This variety is the most hardy and well suited for areas that freeze in the winter.
The varieties of clematis determine when or if a person should prune. As group A varieties bloom on old growth, if the old vines with seed buds are cut away at the end of summer, there will not be any growth the next spring. A gardener should prune the vines that have flowered and leave any that have buds on them.
Group B clematis can be pruned in late winter and again after the first blooming to encourage a full second bloom. Dead branches should definitely be pruned away. Group C varieties are the easiest to prune, as a gardener can cut away the old wood without worry given that the flowers grow on new wood. At the end of the growing season, group C clematis species should be pruned to be about 2 feet (60 cm) tall.
