Clematis is a popular and diverse group of flowering vines. Clematis generally requires pruning for optimal health and flowering. The specific timing and technique depend entirely on the variety and its blooming schedule, which is why clematis are categorized into three distinct pruning groups. Pruning at the wrong time for a specific group will remove the flower buds, resulting in a year without blooms. Understanding which group your vine belongs to is the most important step in its care.
Pruning Clematis Group 1
Group 1 clematis includes the earliest-blooming varieties, such as Clematis alpina and Clematis montana. These varieties produce flowers on “old wood” grown in the previous season, meaning they require the least regular pruning. The goal of pruning this group is maintenance, shaping, and size control, not stimulating new growth for flowering.
Pruning should be done immediately after the plant finishes flowering in spring, typically in late spring or early summer. This timing allows the vine to develop new growth throughout the summer, which will host the following year’s flower buds. The technique involves removing any dead, damaged, or weak stems down to the base.
For shape and size control, stems can be lightly trimmed back to a healthy bud or side shoot. Avoid severe cutting or hard pruning, as this eliminates the old wood responsible for the next season’s flowers. For severely overgrown plants, a rejuvenation cut can be performed, limited to cutting back only one-third of the oldest stems over a few seasons.
Pruning Clematis Group 2
Group 2 clematis, often large-flowered hybrids like ‘Nelly Moser’, exhibit a dual blooming habit requiring a two-stage pruning process. These vines produce a spectacular first flush of flowers in late spring on old wood, followed by a second, lighter flush later in the summer on new growth. The main woody framework must be preserved to ensure the early bloom.
The first, light pruning should be conducted in late winter or early spring, just before new growth begins. Focus on removing any dead, diseased, or weak stems that did not survive the winter. Trace each stem back and prune just above a pair of strong, healthy buds. This early pruning prevents spindly growth and encourages a robust start to the season.
The second stage occurs immediately after the first flush of flowers fades in early summer. This involves a light trim, shortening the flowered stems by about one-third to the next healthy bud or shoot. This action removes spent flowers, prevents the plant from using energy on seed production, and encourages new shoots that will host the second round of blooms.
Pruning Clematis Group 3
Group 3 clematis comprises late-flowering varieties, such as Clematis viticella and ‘Jackmanii’, which bloom exclusively on “new wood” produced in the current growing season. This group is the simplest to prune, but the method is the most severe. Hard pruning is required because leaving the old growth results in a tangled, top-heavy mess with flowers only at the top.
Pruning must be performed in late winter or early spring, typically in February or March, before the plant breaks dormancy. This timing redirects the plant’s energy into generating vigorous new stems from the base. Failure to hard-prune this group results in a heavy accumulation of old, non-flowering wood over time.
The technique involves cutting all stems back drastically to the lowest set of strong, visible buds. This cut is typically made 12 to 18 inches above the ground. Although this may feel drastic, it is necessary to stimulate the new growth that will carry the mid-to-late summer flowers.