Question
For some reason, both of my clematis plants got off to a very fast start this spring  They are now well above the top of the trellis and beginning to curl on the inside of my awning
Would it be harmful (or helpful) to start pruning the tops of these vines for control?

Thanks for your help

Carl Meyers     Wexford PA

Answer
Hi Carl -

Short answer: for controlling the vine's growth habit, you can probably prune the tops whenever you like.

Long answer: In general, the timing for pruning clematis (in terms of truly cutting them back and shaping them) really depends on what kind of clematis you have. There are three pruning groups, but the best rule of thumb is to prune them right after they've finished blooming. Pruning the tops of the vines for control purposes is probably okay now, but just know that you might be cutting back some of the buds. Here is a helpful web site for determining which group your clematis is in.
http://gardening.about.com/od/perennials/a/PruningClematis.htm

That said, I have a spring-blooming clematis, and although the "rule" is to prune this plant in July, I typically wait until later in the year and the vine just keeps chugging along, producing flowers just fine.
Hope this helps.