Clematis are normally divided into three groups as far as pruning is concerned. The grouping reflects their time of flowering and the best way to prune them to achieve the maximum number of flowers. Group 1 consists of those that flower on the previous season’s wood and so require little or no pruning (or the flowering wood will be removed). The typical clematis in this group is Clematis montana and its cultivars. Several other species also fall into this category.
Pruning Clematis Group 1
1: Clematis in this group can largely be left to their own devices in terms of pruning, but some, especially C. montana, can get very congested and over-heavy.
2: Little new growth on this clematis needs to be removed, except for a few straggly growths or where the climber is starting to outgrow its position.
3: The surface of the climber looks almost the same, but beneath it is likely to be a tangle of dead wood, which will need removing.
Initial pruning and training
Plant the clematis deeper in the soil than it was in the pot. The pot soil line should be about 5cm (2in) or more below the level of the ground. This is to ensure that if the plant suffers from clematis wilt, there will be some adventitious buds that will throw up new shoots and so ensure the plant’s survival. Little initial pruning is then required other than to remove any damaged wood. You also need to make sure that the shoots are well spread out and tie any new ones in to a fan shape so that the whole of the support will be covered.
This is the easiest clematis group in that theoretically no pruning is required, as the flowers are formed on the previous year’s wood. However, it is prudent to cut out any dead wood, as this can quickly build up, especially on C. montana. This accumulation of dead wood will not only stifle the clematis, making it look like a vast bird’s nest, but it will also create a tremendous weight that may well bring down the support. So, at least every couple of years, go through the climber and take out any dead wood you can find – a tedious job but worth doing. If the clematis grows beyond its bounds, there is no harm in cutting off the offending shoots at any time of the year as long as you cut back to a strong bud.
C. montana, in particular, can become very overgrown and full of dead wood if it is not regularly maintained. At some point, you will inevitably have to prune it severely to bring it back under control, which is a satisfying task. Fortunately, C. montana can be cut back very hard and will still rejuvenate, so after taking out all the dead wood, cut back into the older wood, leaving some of the younger shoots. If extreme action is called for you can cut it back almost to the ground. All this should take place immediately after flowering.
Group 1 clematis
All the cultivars of the various species below also belong to Group 1.
- C. alpina
- C. armandii
- C. cirrhosa
- C. macropetala
- C. montana
How to prune Clematis group 1
In this group the flowers are formed on the previous year’s wood, so a harsh pruning will remove these and hence its ability to flower in the current year. This group needs very little pruning other than that required to keep the plant under control and to remove any dead wood that may accumulate. The latter will tend to build up, making the plant very congested.