How to Prune Clematis Plants

Base pruning technique on when the plant blooms

Clematis
pritisolanki / Pixabay / CC By 0

Clematis plants include some of the most spectacular garden flowers, including climbing vines and clumping, spreading plants that feature some of the largest, most colorful flowers to be found. These flowering vines can be worked over an arbor, threaded through other perennials, secured up a tree, and some varieties work best when left to sprawl over the ground in low-lying mounds. Growing them is fairly easy, but pruning clematis tends to instill fear in the stoutest of gardeners. This fear is unwarranted since pruning clematis simply breaks down to a question of when your clematis blooms. Like many large-flowered garden species, clematis vines are usually pruned to encourage new growth, which results in more flowers. No matter which pruning category your clematis plants fall into, flowering will diminish on all clematis vines if you don't prune them. Left unpruned, the new growth (and all new flowers) will remain confined to the tops or ends of the vines.

When to Prune Clematis Vines

The proper time to prune clematis plants depends on whether the plant flowers on "old wood"—the growth that was put onto the plant during the previous growing season, or "new wood"—the growth that appears during the current growing season. The goal is to make sure that you don't prune in a manner that eliminates or reduces the flowers, which is why we grow clematis.

Clematis varieties that bloom on old wood should be pruned immediately after they are done flowering, which gives the plant plenty of time to grow new stems, which will become the old wood next spring. Varieties that grow on new wood are best pruned when the plant is dormant—either in the late fall and winter or very early in the spring before new growth has begun.

Project Metrics

  • Working time: Less than 1 hour to prune a single plant
  • Material cost: None; unless you need to buy a pair of pruners

What You'll Need

Equipment/Tools

Instructions

There are three categories of clematis for pruning purposes:

  • Group 1: These are early spring bloomers that flower on previous year's growth (old wood). These are done blooming by mid- to late-spring. Popular varieties in this group include: C. armandii cultivars, C. montana cultivars, and C. apina cultivars.
  • Group 2: These are spring- and early-summer bloomers that produce flowers on previous year's growth as well as on new growth. Most of these are hybrids with very large flowers. Popular varieties in this group include a very large group of cultivars of the Clematis patens species, including ' 'Nellie Moser,' 'Princess of Wales,' and many dozens of others. These are the plants that many people think of when they hear the name Clematis.
  • Group 3: This is a later-flowering group, producing flowers on growth from the current season in late summer and fall. Popular varieties include hybrids such as 'Jackmanii,' ‘Ernest Markham’ and ‘Comtesse de Bouchaud,' as well as species such as sweet autumn clematis (C. paniculata).

If you don’t know which pruning category your clematis falls into or maybe even what type of clematis it is, watch the plant for a season and take note of when and how often it blooms.

Pruning Early Spring-Blooming Clematis (Group 1)

This is a group that can be left unpruned on some years without too much bad effect, but when you do prune them, do it as soon as they finish blooming in the spring. These plants flower on old wood developed during the previous growing season, so you want to give them as much time as possible to develop new wood that will become next year's old wood. This generally means they should be pruned before the end of July.

  1. Remove any dead or damaged stems. While it is generally good to leave the larger, woodier stems, those that are damaged or dead should be removed all the way to ground level.
  2. Inspect the remaining stems for emerging buds. If you see these, it is the wrong time to prune, and you should probably wait until after the plant has finished blooming for the current season.
  3. Use bypass pruners to clip off the undesired growth. This can involve trimming off unruly outer stems back to woody main stems or trimming some shoots off near ground level. How you prune is really a matter of how you wish to shape the plant.

How to Prune Spring- and Summer-Blooming Clematis (Group 2)

Sometimes described as repeat bloomers, clematis varieties in this group generally produce a heavy flush of flowers in spring, but then will rebloom in smaller quantities later in the season. Plants in this group include many with the largest, most dramatic flowers. With these, annual pruning is essential, as without it the plants will get very top-heavy and have fewer flowers. These plants flower on both old and new wood.

  1. In late winter or very early spring, trim away all damaged or weak stems down to ground level.
  2. Trim remaining stems back to a point just above the strongest, most visible buds.
  3. After the first heavy bloom is completed, prune the stems again, this time back to a pair of buds about halfway down the stems. Pruned this way, you often will get another period of blooming on new wood in late summer or early fall.

How to Prune Late-Blooming Clematis

The late-flowering group produces flowers on the current season’s new growth, which requires a different approach to pruning. These plants, including some popular varieties such as sweet autumn clematis (Clematis terniflor or C. paniculata), typically die back to ground level in the winter, and any old plant material left in place creates a disheveled mess.

In late winter or very early spring, cut these plants down to about 2 feet from the ground. Most of these are very vigorous growers—sometimes bordering on invasive—so be aggressive about pruning, and make sure to do it each year.

Tips for Pruning Clematis

  • Slower growers should be treated more cautiously, pruning just enough to shape the plant or to keep it in bounds. The faster a clematis grows, the more aggressive you can be with pruning.
  • Don't be afraid to ignore pruning duties until you've witnessed a season or two of growth. Once you know what type of clematis you have, it will become clear what pruning strategy to employ.
  • A few heavy, established stems can be left in place, even for varieties that bloom only on new wood. These stems form a framework around which new wood can grow.