Guide to Clematis Pruning
Regardless of species or cultivar, clematis belong to one of three pruning groups based on when they bloom. Each group requires a slightly different approach to the pruning, which is needed to remove dead, diseased or damaged stems, promote branch strength, good air and light penetration and an abundance of new bud-laden stems. Pruning is also needed to check the growth of fast, aggressive growing varieties before they become overgrown in the garden.
Most clematis will take three growing seasons to establish after planting. During this stage little pruning will be needed and only the removal of dead, damaged or diseased stems. By the fourth season heavier pruning usually begins.
Group 1: Spring Blooming Cultivars – These plants bloom on old wood – the previous season’s growth.
- Prune young plants lightly after blooming to encourage well-branched stems. This is best done as flowers fade to allow time for the new wood to ripen (develop dormant buds for next spring.)
- Prune older plants more heavily, again after blooming ends. Remove enough wood to prevent vines from overgrowing their support and thin congested areas to allow for sunlight and air to penetrate.
How hard to prune will depend on the vigor of the cultivar. Fast growing plants need harder pruning than slower growing selections. Older vines, and those that have been neglected and are producing fewer flowers need rejuvenation by hard pruning back to some of the oldest stems available. This is always best in early May to take full advantage of the spring flush.
Group 2: Spring and Summer Blooming Cultivars – These plants bloom on both old and new wood.
- Sometimes referred to as Repeat Blooming, and can depending on cultivar:
a) Bloom on old stems first then bloom a second time on new growth in late summer.
b) Bloom on both old wood and new growth at the same time creating continuous flowering.
- Prune Group 2 types lightly in spring, to encourage the formation of new stems and buds for later blooming, promote more branching and to open plants up to air and light. Keep enough old wood to provide strong spring flowering, while the new growth matures.
An easier approach for Group 2 types is to hard prune vines in early spring every two years. This will sacrifice the spring display of flowers. Most clematis varieties grown in Canada belong to this group.
Group 3: Summer and Fall Blooming Cultivars – These plants flower late on new growth only.
- Prune Group 3 vines back hard to two or three nodes, up to 12-inches from the ground. Plants will recover and begin blooming in mid-summer through fall.
- These are among the easiest vines to grow.
- Species type clematis belong to Group 3 and are often used on large supports like arbors and pergolas or allowed to scramble through larger shrubs and trees.