There’s a lot to like about clematis, one of the earliest vines to green up in the spring. It’s easy to grow, blooms in profusion and is hardy, with some varieties lasting more than 50 years. Yet there remains a great deal of confusion about when — or even if — these woody plants should be pruned.
“If you have vines that grow 20 feet a year, they likely will be blooming in your neighbor’s yard and not your own,” said Linda Beutler, curator of the Rogerson Clematis Collection at West Lynn, Ore., and author of “Gardening With Clematis” (Timber Press, 2004). “The reason for pruning is to keep them under control.”
There are more than 250 clematis species and even more hybrids. They are separated into three broad pruning groups, mainly according to when they bloom; if you know your cultivar, you can find its group on the Internet.
Clematis in Group A are the spring-blooming varieties that flower on stems produced the previous season, the “old wood.” Some experts say to prune them soon after blooming.
Group B is the large flowered hybrids. They bloom in early to mid-summer, also on old wood. Prune the tops of these plants lightly in February or March. The vines can be given a second and hard cutting immediately after flowering, down to a height of around 18 inches.
Group C is the late bloomers. They bloom on stems formed during the current growing season, and should be pruned in late winter or early spring.
But Denver Post Grow columnist and Front Range gardening expert Marcia Tatroe largely stopped keeping track of pruning groups. She prunes most of her vines to a foot tall in early spring: “Spring bloomers get underway later in the season, true, but it beats having to untangle dead vines from live,” she wrote.
So if you don’t know your clematis cultivar, don’t fret. There are many ways to kill clematis, but pruning isn’t one of them, Beutler said.
“Even if you prune at the wrong time, the only thing that will happen is that you’ll set the blooms back by a year.”
The Denver Post contributed to this story.
