There are numerous clematis species, hybrids and cultivars, but for pruning purposes they are split into three distinct pruning groups based on the time of flowering and the age of the flowering wood.

Clematis in pruning group two are the large-flowered cultivars that flower in May to June on short shoots developing from the last year’s growth. Some flower again in late summer on new growth.

Examples include of clematis in pruning group two include:

'Barbara Jackman'
'Bees' Jubilee'
'Belle of Woking'
'Beauty of Worcester'
'Burma Star'
'Doctor Ruppel'
'Duchess of Edinburgh'
'Edith'
Clematis florida var. sieboldiana
'Jackmanii Alba'
'Jackmanii Rubra'
'Marie Boisselot' AGM
'Matka Teresa'
'Nelly Moser' AGM
'Snow Queen'
'The President' AGM
'Rebecca'
'Royal Velvet'
'William Kennett'

Prune in late winter or early spring (February) and after the first flush of flowers in early summer.

The aim with pruning group two clematis is to retain a framework of old wood and also to stimulate new shoots in order to maximise flowering throughout the season.

Initial pruning and training

If young clematis are left unpruned they often produce very long single stems with the flowers produced only at the very top.

Unless the plant already has three or four healthy stems growing from the base, all newly planted clematis should be pruned back hard the first spring after planting. Cut back to just above a strong pair of leaf buds about 30cm (1ft) above soil level. This will encourage multiple stems which can be trained in to supports to give a good coverage.

During the spring and summer, tie in new growth, spacing stems evenly on the support.

Pruning established plants

Prune in late winter or early spring (February) as follows:

• Remove dead or weak stems before growth begins. Check individual stems from the top down until you reach a pair of healthy buds, and prune just above them, removing the spindly or damaged growth above
• Avoid heavy pruning or flowers will be lost

Then prune again after the first flush of flowers:

• To encourage a second flush of flowers later in the season prune back some stems by cutting to large buds or a strong side shoot immediately below the blooms
• Top-heavy or overgrown plants can be gradually reduced over two to three seasons by pruning back harder after the first flush of flowers. They are unlikely to produce a second flush of flowers, but should flower again the following year, in late spring or early summer

Alternatively, leave clematis in this group unpruned, and then hard prune them to 30-90cm (1–3ft) from the base every three or four years in late winter (as for pruning group three). In the first year after renovation, they will only flower once.

Some mid- to late summer flowering clematis can be treated as either pruning group two or pruning group three, as desired. Examples include: 

'Comtesse de Bouchaud' AGM
'Gipsy Queen' AGM
'Hagley Hybrid'
'Jackmanii' AGM
'Jackmanii Superba'
'John Huxtable' AGM
'Perle d'Azur' AGM
'Rouge Cardinal'
'Star of India'

Links

Clematis pruning: group one
Clematis pruning: group three