Pruning a Clematis Vine

A clematis in full bloom will catch any ones eye, they are spectacular. The full color pictures we see in catalogs are fantastic, big blossoms with bold colors. Yet, many of us have experienced the dark side of clematis - a tangle of woody stems, bearing just a few spindly flowers. The question then is how do you get a clematis to bloom with abundance? The secret is in the pruning. However, pruning is complicated and a puzzle for many.

Before you begin to prune a clematis, you will need to know which pruning group your clematis belongs to: A, B, C, . If you don't know, I suggest you put your pruners away and just watch your plant for a year. During this time, first pay close attention when your clematis blooms - spring, summer, fall, or late winter. Second, (now this is where the pruning instructions get complicated.) note whether it blooms on woody stems that grew last year (old wood). Or does your clematis bloom on green stems (new wood) that grew in the current year as do butterfly bushes and roses. Once you have this information, you will be able to determine which group your clematis belongs: A, B, or C.

Group A contains all the clematis that bloom on new green stems (new wood) and flower in summer and autumn. This group includes 'Ville de Lyon', 'Jackmanii', 'Sweet Autumn', 'Crimson Star' and many others. Group A clematis are easy to prune. With this group you have to be ruthless for these varieties to shimmer with flowers. Each year, in late February and early March, cut back all the stems virtually to the ground (1-2 feet above the soil). Make each pruning cut above a strong set of buds. That's it!

Group B contains varieties that bloom in spring between April and June. They bloom on woody stems that grew last summer (old wood). This group includes 'Elsa Spath', 'Nelly Moser', 'Ruby Glow', 'Henryi', and the 'President' to name just a few.

The growth habit of group B plants makes it difficult to prune satisfactorily without a great deal of hassle.

For Group B, a renewal pruning is really the best strategy if you want abundant flowers each year. Renewal pruning is removing one-quarter to one-third of the oldest branches to within one to two feet above the ground. The renewal technique is a hassle, because once you cut a stem you still have to untangle it from the remaining branches. Renewal pruning is done soon after the plant has finished blooming.

If your not confused yet, there is Group C. This group contains evergreen clematis such as Clematis armandii. These clematis bloom in late winter and early spring on stems produced the previous season (old wood). Wait to prune group C until after they have bloomed. This group generally only needs enough pruning to keep it tidy. But, if your evergreen clematis is not flowering, or has overgrown its trellis, it is time for a renovation pruning. After flowering, prune out almost all of the side branches, leaving only the main vertical stems that attach to the trellis.

My last tip for success with clematis is this - clematis climb a trellis by twisting leaf petioles, the vine itself does not twine as does a honeysuckle vine. Be sure your trellis is not made of material larger then 3/4 of an inch in diameter. A clematis is unable to grasp onto materials greater than 3/4 inch. If your trellis material is too large, you have to manually tie the vine to the trellis. This means just a lot more work for you!

Author Mary Jo Buza, is a landscape designer and owner of Gardens by Design. She has 25 years experience maintaining, designing, and teaching gardening in the South Sound region. For more information on a custom landscape design or consultation call 923-1733.