Lincoln Star and Daniel Deronda are both large-flowered Group B clematis.

The ABCs of Clematis

by Vonnie Kovacic
Images © Vonnie Kovacic

Okay, so you have just purchased a new home that includes a clematis that’s outgrown its trellis.

Or maybe you have taken a page from my book: you buy and plant clematis then lose or forget it’s name and/or cultural requirements. So now they need to be pruned... the question is when?

No, guessing isn’t necessary! Clematis can be divided into three different types and observing when a clematis blooms enables one to prune the vine correctly.

Group A clematis: This group blooms in early spring on growth that was produced the previous season. Cut the stems back sharply right after blooming but no later than July. The plant needs plenty of time to produce new wood for next year’s flowers. Varieties of C. alpina with their lovely nodding, lantern-shaped blossoms fall into this category. The fragrant C. montana is another A type.

Group B clematis: These clematis flower twice a year. The first blooms are early in the spring on last year’s growth, then they re-bloom in late summer on stems produced during the current season.

Clematis florida Seiboldii blooms later than most and resembles a passion flower with its central clusters of purple, petal-like stamens.

Prune this group by removing all the dead and weak stems in early March and shorten the rest of the vines by about 10 inches, just above a strong pair of leaf buds. Now re-tie the remaining stems back where you want them to grow. Many of the large flowered types of clematis are in the B group.

Group C clematis: These varieties produce blooms on new stem growth every year. Each spring (March) all of the stems should be cut back to within 30 inches of less of the soil level, just above a strong pair of buds.

Most clematis in this group bloom in late summer or fall and include some interesting vines - varieties of C. texensis, C. viticella and several species.

So, what happens if you get carried away and prune a clematis at the wrong time? Not much. At the very worst you will lose one season of blossoms.

Sometimes the vines become so vigorous and tangled that there is no other alternative but to get in there and hack away. For example, C. armandii and C. montana are two clematis that just don’t know when to stop growing.

On the other hand, if you never get around to pruning your clematis they will still grow and flower, but perhaps with less vigor and size. Few plants are so carefree, colourful and adaptable. Every garden should include a vine or two.

Coquitlam resident Vonnie Kovacic has a passion for propagating plants from seed and cuttings. She is a contributing writer to GardenWise magazine.