Posted: 22/12/2013 at 13:07
This may help
Clematis is a beautifully varied flowering plant, available in a multitude of colours and flower sizes, however all Clematis fall into one of 3 distinct pruning groups: No Prune (Group 1), Light Prune (Group 2), and Hard Prune (Group 3).
Group 1: Early Flowering. Typically blooming in winter and spring, these varieties flower on the previous year's growth only, so if you need to remove damaged stems or control the size of the plant, the best time would be as soon as they have finished flowering. Included in this group are Alpina, Macropetala, Montana, and Evergreen varieties.
Group 2: Large Flowers. Typically larger flowers grow out on new shoots from last year's growth in late spring and summer. Some of these will occasionally display a second bloom at the tips of the current year's growth in late summer and autumn. These varieties should be pruned in spring, right back to where there are strong and healthy buds, before they start their active growth period. New flowering stems will be produced from this architecture of previous growth.
Group 3: Late Flowering. Group 3 Clematis only flower on current year's growth. These blooms tend to display from summer through to late autumn. These varieties are arguably the easiest to prune, as you basically cut it right down to about 20cm (8ins) above ground level in spring before they begin their active growth period, removing all of the previous year's growth.