When do I prune my clematis?
That depends on the type of clematis you have. Clematis fall into three pruning groups based on their flowering characteristics. When you purchased your vine, there should’ve been a tag indicating whether it belongs to pruning group A, B, or C. However, as long as you know the cultivar name, you can easily look this information up.
If you've inherited a vine or have forgotten the variety you planted, the following is a general guideline for pruning.
If you have a clematis that flowers early in spring (Group A) then wait until it has finished flowering to cut it back. Since this group flowers on old wood, try to prune it as soon as you can after flowering so that the vines have time to mature by next spring. Delay pruning and you could end up looking at a leafy green, flower-free wall next year. The problem will correct by the following year as long as you don’t inflict another pruning on it. Pruning is optional for Group A clematis and is usually done only for maintenance purposes.
A clematis that blooms in the spring then sports a second flush later in the season (Group B) needs only moderate pruning. That first, prolific flush of flowers appears on old growth and the later, more conservative flush appears on new growth. The best time to prune these vines is in early spring, but only if they need reshaping. If you prune moderately, you'll preserve the vine’s natural flowering characteristics. Alternatively, you can cut the vine back to just six or eight buds and get a single stunning flush of flowers later in the season.
If your clematis blooms in the summer and continues blooming sporadically into the fall (Group C), it needs to be cut back hard early every spring since the flowers only form on new growth. Take the vines down to six to eight buds and they will fill the trellis with blooms later in the season.
It can be difficult to distinguish between pruning Group B and Group C and sometimes a little trial and error is involved. The biggest reason why a clematis doesn’t flower is because it's been pruned incorrectly. If a variety that blooms only on old wood is cut back hard in the spring - or if a variety that blooms on new wood isn't cut back at all - then you end up with very few flowers and sometimes none at all.
If you don't know which kind of clematis you have, then don't do anything for a season. If it does nothing or only has a few flowers at the tips, it's probably a variety that blooms on new growth and needs to be cut back hard every spring.
If you have any questions or comments, please send them to me at vanessa@gardenmuse.ca.
