How & when should I prune my Clematis?

Pruning controls the height & spread of the plant & helps to keep the plant healthy, a reasonable size & the flowers at eye level. Obviously if it is a stronger growing variety climbing up through a tree then pruning will not be possible. These varieties are natural scramblers & will continue to perform without any pruning being necessary. Unfortunately, Clematis do not all flower at the same time during the season. Their flowering times dictate their pruning requirements which are divided into 3 categories.

The categories are: Early season flowering ( winter to late spring), these varieties fall into pruning group 1. Mid-season flowering (late spring to early summer) pruning group 2. Late season flowering (midsummer to autumn) pruning group 3.

Buying a Clematis – Look for a healthy looking plant with some strong stems & a good quantity of leaf buds at soil level.

Planting a Clematis - With large flowered Clematis the rootball should be planted about 10 cm deeper than it was in the pot so that new shoots are produced below soil level to try to ensure against Clematis wilt. Species Clematis don’t tend to suffer from Clematis wilt. All Clematis should be hard pruned to about 30 cm above soil level in the spring following planting. This ensures good, bushy growth & a strong framework. If you do not do this then 1 or 2 stems will romp away to about 2 m or even longer & make a tangled mess leaving bare stems below. From the second spring after planting carry out the annual pruning requirements for your variety to ensure optimum flowering.

Pruning group 1 ( Early season flowering – winter to late spring) this group includes C. montana & montana var. grandiflora, C. macropetala, C. alpina, C. armandii, C. cirrhosa & their cultivars. Remove dead or weak stems immediately after flowering. Trim lightly & tidy if necessary. After pruning you should see new growth appearing, this ripens as the season progresses & will produce the flowers next year. For C. montana cultivars they can be regularly trimmed until June if they need to be kept in check. Stop pruning in June so that it can make new growth & ripen wood to produce flowers for the following year. With C. alpina, C. macropetala, C. cirrhosa & their cultivars you may need to remove some of their older growth completely at this time to regenerate the plant enabling it to produce new flowering growth for the following year.

Pruning group 2 (Mid-season flowering - late spring to early summer) this group includes large flowered hybrids such as ‘Nelly Moser’, ‘Lemon Chiffon’, ‘Barbara Jackman’, ‘Pink Fantasy’, ‘Burma Star’, ‘Fuji-musume’. ‘H.F.Young’ & all other large flowered Clematis that flower at this time of year. Remove dead & weak stems in  spring. The rest of the pruning can be done at this time or up to early summer. Lift up the tangle of wiry stems & remove any dead foliage. Locate the new strong, newly emerging fat leaf buds & trim back to them.

Select 2 or 3 of the weaker stems & prune them back to between 30-60 cm from the base to stimulate fresh growth from the base of your plant. Finally, tie in the remaining stems to prevent wind damage.

Pruning group 3 (Late season flowering – midsummer to autumn) this group includes Viticella cultivars & late large flowered hybrids such as C. ‘Perle d’Azure’, ‘Hagley Hybrid’, ‘Jackmanii’, ‘Etoile Violette’, ‘Royal Velours’ & any other Clematis that flower from midsummer to autumn. These Clematis flower on new wood each year so pruning is straightforward. In late winter cut off all the previous year’s tangled growth to about 30 – 45 cm above soil level. This will stimulate new basal growth. If you prune too early the new growth might be damaged by cold frosts so check the new growth regularly, tie it in evenly around the support. Listen to the weather forecasts for your area so that you don’t prune too soon.  Boulevard Clematis are compact, free flowering varieties ideal for smaller gardens or pots. They need to be pruned as late-season varieties to keep them bushy. In spring hold all the stems up together in one hand & cut off all the stems to about 30 cm above soil level.

As a general rule – if the plant flowers before the end of June just give it a light tidying. If the plant flowers after the end of June prune harder.

Orange-peel Clematis cultivars flower profusely with silvery seed heads following the flowers. C. tangutica & C. tibetana subsp. Vernayi (C. orientalis) need to be pruned as Group 3. However check the plant in spring – if there are signs of new growth remove the tangled mess being careful to avoid damaging the new shoots. Remove all dead & weak stems & prune any strong stems down to about 45 cm just above a bud. Carefully tie new growth to the support. Delay pruning if no new growth is visible otherwise water might penetrate the fibrous stems & cause splitting & dieback.

Pruning herbaceous Clematis – Treat like a herbaceous perennial & cut back to or near to  ground level because the new growth comes from the base of the plant. As new shoots appear remove the previous year’s growth. If you have a heracleifolia variety prune to just above a strong bud about 10 cm above ground level.

Pruning Clematis growing through a shrub – When planting make sure you match the vigour of the Clematis to the shrub so that it does not swamp the shrub. Clematis can be planted through shrubs that flower in winter like Lonicera purpusii ‘Winter Beauty’or shrubs flowering in spring to give summer interest. They can also be planted to scramble through shrubs with coloured foliage or planted with shrubs such as roses to flower at the same time. The Clematis might need to be tied in to prevent damage to its stems.

Cath’s tips.