Clematis are popular climbing vines known for their abundant, colorful flowers, but deciding whether to cut them back for winter depends entirely on the specific variety you are growing and when it naturally blooms. Applying the wrong winter cutback can eliminate the following season’s flowers. Therefore, you must first determine which of the three main pruning groups your clematis belongs to before deciding on any winter maintenance.
Understanding the Clematis Pruning Groups
The classification of clematis into three distinct pruning groups is based on the time of year they flower and the age of the wood on which they produce those flowers. This system helps gardeners ensure they do not accidentally remove the buds needed for the next bloom cycle. Group 1 clematis are the earliest bloomers, typically flowering in late winter or early spring on growth from the previous year, often called old wood. These varieties, such as Clematis montana and Clematis alpina, require little routine pruning.
Group 2 varieties are large-flowered hybrids that bloom in late spring to early summer on old wood, often followed by a second, lighter flush of flowers in late summer on new growth. The first bloom relies on stems that survived the winter, requiring careful treatment to preserve them. These mid-season bloomers are complex to manage because they use both old and new wood for flowering.
The third group, Group 3, is composed of late-flowering varieties that produce blooms exclusively on the current season’s growth, or new wood. These clematis typically flower from mid-summer through late autumn and include types like Clematis viticella and the popular ‘Jackmanii’ hybrids. Since the plant produces all its flowers on growth that emerges in the spring, the old stems from the previous year are not needed to support the next bloom.
Specific Winter Pruning Guidance by Group
Winter pruning guidance varies dramatically across the groups, ranging from no cutback to a near-complete reduction of the vine. For Group 1 clematis, which flower on old wood, avoid winter pruning entirely to preserve the flower buds set the previous year. Any necessary pruning, such as removing dead wood or controlling size, should be carried out immediately after they finish blooming in late spring or early summer.
Group 2 clematis also require that their old wood be preserved, so heavy winter pruning is not recommended. Instead, in late winter or very early spring before new growth begins, you should only perform a light, maintenance trimming. This involves carefully removing any obviously dead, diseased, or damaged stems down to a healthy pair of buds. This minimal approach retains the framework of old stems needed for the first flush of flowers.
Group 3 clematis should be cut back hard during the dormant period in late fall or late winter. Since they flower solely on new growth, a severe cutback encourages vigorous new stems and prevents a tangled mass of old wood. You can cut all stems down to about 12 to 18 inches above the ground, making the cut just above a strong set of buds. This dormancy pruning promotes lush growth and abundant flowers.
Preparing Clematis for Cold Weather (Non-Pruning Steps)
Regardless of the pruning group, a few general steps help prepare the clematis for the stresses of cold weather. A primary concern is protecting the plant’s crown, which is the point where the stems meet the roots just below the soil surface. Applying a thick layer of organic mulch, such as straw, shredded leaves, or wood chips, around the base of the plant once the ground has frozen helps insulate the roots from extreme temperature fluctuations. This mulch layer should be 4 to 6 inches deep and should extend outward from the crown to cover the root zone.
For clematis grown in containers, additional insulation is necessary because the roots are exposed to freezing air temperatures. Move container-grown plants to a sheltered location, such as against a south- or west-facing wall, or a cool garage. If the pot must remain outdoors, insulate it by wrapping the container in burlap or securing a layer of dry leaves around it to protect the root ball from freeze-thaw cycles.
Maintaining proper soil moisture is also important, even when the vine is dormant. While the plant requires less water in the fall, it is beneficial to give the clematis a deep soaking before the first hard frost. Ensuring the soil is not waterlogged is equally important, as poor drainage combined with freezing temperatures can cause the roots to rot. Finally, clearing away any fallen leaves or plant debris from around the base of the vine helps prevent pests and fungal diseases from overwintering near the plant.