- Written by Robbi Hoy
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Clematis can be a confusing group of plants to prune because they're not all pruned at the same time. If you watch your Clematis and learn the time of year it blooms, you can quickly learn when to prune.
Back in the 1950's loosley defined groups were created to help Clematis fans learn when to prune. We now group them into 3 groups which for the purpose of this article we'll call Groups A, B and C.
This Clematis is usually the earliest flowering and bloom on old wood (last years stems). They prefer a sheltered sunny sight with well drained soil and bloom in late winter to early spring (depending on your zone).
This group has single flowers that are bell shaped or open bell shaped, 3/4-2in (2-5cm) long, or saucer shaped, 1 1/2-2in (2-5cm) across. They require very little pruning. Pruning should be limited to removing dead stems. If you need to, after blooming, prune out select vines to control size or shape but avoid cutting far into the main woody trunks.
Some Clematis included in this group are: C. alpina, C. macropetala, C. armandii, C. montana, and C. chrysocoma
Clematis in group B are early to mid-season, large flowered species and cultivars. They bear flowers in late spring and early summer on sides hoots that come from from last year's growth. In late summer they bloom at the tips of this year's shoots. They prefer a sheltered sunny sight with well drained soil and produce flowers that are upright, single, semi-double or fully double; and mostly saucer shaped, 4-8in (10-20cm) across. Prune this Clematis lightly in late winter or early spring when buds begin to swell. Leave the best of last year’s buds. Once they finish blooming, deadhead all bloom stems or cut the plant back to 12-18in (30-45cm) to force new growth for a second round of flowers.
Some Clematis in this group are: The President', 'Vino', 'Countess of Lovelace', 'Anne-Louise', 'Arctic Queen', 'Bees Jubilee', 'Crystal Fountain', 'Duchess of Edinburgh', and 'Rosemoor'.
Clematis in this group are late flowering, large and small flowered cultivars and species. They bear flowers on the current year's shoots in summer and early autumn. The large flowered cultivars are single and outward facing, usually saucer shaped and 3-6in (7-15cm) across. The small flowered Clematis in group C are single or double, and can be saucer shaped, star shaped, bell shaped, open bell shaped, tulip shaped or tubular. They can be 1 1/2-4in (1-10cm) across. These Clematis are the easiest to prune but also the Clematis with the greatest need of hard annual pruning. In late winter or early spring, cut the Clematis back to 24-36in (60-90cm) since no old wood needs to be maintained. Cut to a pair of healthy strong buds at the base of the plant. If these go unpruned, the flowers are produced way up at the top of the plant making them appear leggy. This group also includes some of the non-vining clematis such as Clematis durandii.
Some common Clematis in this group are C. x jackmanii, C. viticella, C. flammula, C. crispa, ‘Royal Velours,’ 'BillMackenzie', and ‘Duchess of Albany’