(Editor's Note: This article was originally published on March 24, 2010. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)

Be reassured that incorrect pruning will not bring about the early demise of your beautiful bloomer. In fact, there are times--such as when you are training a newly-planted clematis, rejuvenating an old one, or removing stems affected by disease--that beg for a little tough love with the clippers. Even if you do prune a clematis too much or at the wrong time, the worst case scenario is that it will not bloom until the next year.

Most gardeners have heard that timing of clematis pruning depends on whether the vine is categorized as part of group 1, 2 or 3 (the groups are also sometimes labelled as A, B and C). So how do you know what kind you have? Many of the clematis sold at nurseries today have the group number displayed right on the plant tag. If you know the name of your clematis variety, you can look it up. FineGardening.com provides an useful list of some of the most popular clematis varieties and their pruning groups here.

If you are not sure which variety you have, observe its flower size and blooming habits. Does it bloom early in the season, producing large flowers on brown, woody growth? Then it’s probably in the Group 1 category. If it doesn’t begin blooming until June, and often produces a second crop of smaller flowers late in the season, it’s likely Group 2. And if it has smaller flowers which appear on green stems in summer or fall, it’s most likely Group 3.

Clematis Pruning Tips

• Avoid pruning your clematis late in the season if you live in an area with cold winters.

• You can deadhead early blooming varieties to encourage a second bloom, but you will miss the seed heads which you can enjoy right into winter.

• Always make your cuts just above the fat buds.

• Dispose of clematis clippings in the trash rather than your compost pile, and keep fallen leaves raked up to discourage fungal disease.

Group 1

Group 1 clematis bloom the earliest, between April and June, depending on your zone. This group includes C. montana, C. alpina, C. macropetala and C. armandii. These clematis bloom on old growth--all their flower buds were produced in the last season. Prune these early bloomers very lightly in early spring, moving top down to the highest pair of buds, removing only dead or damaged stems. Any other pruning should be done immediately following blooming, so the vine will have plenty of growing time to produce new buds for the next season. Avoid cutting back the woody stems of any vine in Group 1.

Group 1 Clematis:
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C. alpina 'Pamela Jackman; C.armandii 'Apple Blossom'; C. macropetala 'Blue Bird'; C. macropetala 'Markham's Pink'; C. montana 'Elizabeth'

Group 2

Group 2 clematis are large-flowered hybrids which produce a heavy display in June on old wood, then a second bloom (with smaller flowers) later in the summer on new growth. Hybrids ‘Miss Bateman’, ‘Nelly Moser’ and ‘General Sikorski’ are just a few in this category. Group 2 vines require more early spring pruning than Group 1, but since the majority of the bloom is on old wood, you don’t want to trim away too much. Starting at the top, prune back one stem at a time to a healthy bud. If the vine has become tangled and requires a hard cutting back, the best time to do this is after the first flush of bloom, so the vine still has time to put on growth before the end of the season. Some varieties bloom on old and new wood simultaneously, meaning that they are in bloom almost continuously. It’s always hard to trim away a plant that is blooming, but in the long run you will be rewarded with more flowers on a healthier plant.

Group 2 Clematis:

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C. 'Henryi'; C. 'Multi Blue'; C. 'Nelly Moser'; C. 'Niobe'; C. 'Ramona'

Group 3

These summer or fall bloomers are smaller-flowered and bloom on new growth only, so you will want to prune them hard in early spring, removing all the old growth. C. terniflora (sweet autumn clematis) and hybrids ‘Ernest Markham’ and ‘Comtesse de Bouchard’ fall in this category. Group 3 clematis are the easiest to prune, because although you cut away more of the plant, there is little decision-making necessary. Just be sure you leave two sets of healthy buds on each stem, about 12 to 30 inches above the ground. These vines start their new growth close to where last year’s growth ended. Left unpruned, they will develop long, twiggy stems at the base. If your goal is to have the clematis bloom on a support far above the ground, you might actually want to encourage this.

Group 3 Clematis:

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C. 'Hagley Hybrid'; C. 'Jackmanii'; C. 'Ladybird Johnson'; C. terniflora; C. 'Ville de Lyon'

Training a Young Clematis

Anxious though you may be to see your newly planted clematis bloom for the first time, some patience is required, since these vines need a strong root system to support luxuriant growth. Prune a young clematis back to 18 to 24 inches in its first season, no matter which group it falls in. Doing so encourages branching and will improve the vine’s appearance and flower production in the future.

Rejuvenating an Old Clematis

If you have a clematis so overgrown and tangled that it is no longer blooming and you don’t even know where to start pruning, you can rejuvenate it by cutting it almost back to the ground in very early spring. Within a year’s time, you will once again be rewarded with bountiful blooms. After pruning, a clematis will put on growth quickly, so be sure to keep it watered and fertilized even when it's not blooming.

University of Illinois Extension

Ohio State University Extension

Photo credits:

Title Photo: Clematis 'Jackmanii' by Joy

Other photos: Todd_Boland; bootandall; Shirley1md; kniphofia; DebinSC; handhelpers; tyke; Bug_Girl; kell; victorgardener; TomC_UK; mystic; dinu; Evert