PruningWhile it is not mandatory to prune Clematis, you will find that your plant is more attractive and will produce more flowers if properly cared for. Pruning also enables you to control the size and growth of the plant and allows you to remove dead or damaged parts.Clematis are divided into 3 main groups for the purposes of pruning. These pruning groups are typically referred to as A,B or C. Group B is further divided into two subgroups, B1 and B2.
With new plants, you can determine the pruning group by looking at its tag or label. If the tag is unclear, or has been lost or damaged over the years, you can determine the pruning group by watching the plant over the course of the year and noting its growth and flowering habits. Specifically, you should note when it flowers and whether the flowers form on ´old´ or ´new´ wood.
Old wood is usually defined as plant stems that grew last year, matured and then survived the winter to make it to the present.
New wood is the young, green flexible stems that have grown from the main stems this year.
Pruning Group AClematis in pruning Group A produce flowers in early Spring on old wood, that is, stems produced last year. Plants in this group do not normally require pruning unless you want to control the size and shape of the plant. If pruning is required it should be performed after the plant has bloomed. In our climate (Pacific Northwest), this is usually between May & June. Be aware that pruning after June may reduce the number of next years blooms. Similarly, pruning too early in the Spring (before blooming) will have the same result ? less flowers. You can usually recognize Group A clematis because they do not die back to the ground in winter, and generally bloom in the Spring on old growth.
Common Group A Species & CultivarsC. armandii
Pruning Group BPruning Group B contains some of the showiest and most attractive varieties including large flowered doubles and those that bloom multiple times in one year. Group B is often divided into 2 sub-groups, B1 and B2.
Group B1Clematis in group B1 produce larger attractive flowers on old wood in May or June, followed by a second round of smaller flowers on new wood (stems that grew this year) in the Fall. Some varieties will produce double flowers during their Spring blooming period and single flowers in the Fall. In normal situations this type of Clematis will require maintenance pruning only. Pruning should be carried out in early Spring just as the plant begins to leaf. This will enable you to identify branches that did not survive the winter. Remove dead or damaged stems, trim tips, and thin out congested or tangled areas. If you prune too much, you may affect the quantity of flowers produced this year, so do not cut back any more than necessary.
Common Group B1 varietiesC. florida
Large flowered Hybrid Cultivars including ´Henryi´, ´Nelly Moser´, ´Niobe´, ´The President´
Group B2Clematis in Group B2 produce flowers on both old and new wood simultaneously from June through September. Pruning should take place in late February to March. As with Group B1 or C, you should remove weak, dead or damaged stems, thin out congested or tangled areas and trim back tips. Over pruning will reduce the number of flowers produced but will not hurt the long term life of the plant.
Group CGroup C Clematis produce blooms on new wood - stems grown this year, in early Summer and sometimes through the Fall. These plants die back each year in Winter. In the Spring, the flowers of these plants begin very close to where growth finished last season. Over time flowers will start higher and higher on the plant and a bare section of stem without blooms will begin to appear at the bottom. In order to provide a great show of flowers from soil level and up, Group C clematis should be cut back each year so that only two sets of strong buds are left on each stem. This should be carried out in late February or March. While you do not need to prune group C clematis, a failure to do so will result in smaller and fewer flowers and flowers that form only near the top of the plant. An interesting alternative for these plants is their ability to be used as a ground cover.
Common Group C cultivarsC. tangutica
Growing PainsThere are a few Clematis afflictions to be aware of:
Clematis wilt is a fungal disease most often affecting young plants. The plant seems fine in spring, new growth is produced and long awaited bloom buds are almost ready to burst forth when suddenly the leaves wilt, brown and one or two branches die back, sometimes the whole plant collapses. Fortunately this disease does not often mean the end of the entire plant. If your Clematis does get wilt, prune back and dispose of affected branches, be sure to prune to at least 1 inch below the affected area. Species Clematis seem to be more resistant to wilt.
Powdery mildew in areas of poor air circulation can be unsightly later in the season, but rarely has any bearing on the growth of your plant. Thin branches as needed at pruning time to increase air circulation around plant.
Weevils, Slugs and Earwigs can often be a pain on new plants and lower branches. If they are particularly troublesome in your area, the best method for preserving your plant is the barrier method. Tanglefoot, a sticky paste can be applied on plastic wrap at the base of larger clematis, or onto a plastic container that has had the bottom cut off and is cut to surround the base of smaller plants at ground level. Ensure, also that the area around your Clematis is clear from leaves, branches and other debris, as these are prime hiding grounds for these pests.
Clematis are one of the most versatile family of plants. From groundcover to climber to shrub form perennial you can find an astounding variety of Clematis to suit your needs. There are demure Clematis varieties that can live happily in a container on a balcony and there are other vigorous and prolific climbers that can hold their own in an estate planting. Even in our own increasingly crowded garden, there is always room to get vertical with a Clematis!