The purpose of pruning Clematis montana is not to make it grow. The plant will grow as long as it has food, water and sunlight, regardless of what else you do to it. However, pruning allows you to control the growth for size, shape or schedule of blooms. Clematis plants fall into three categories of pruning needs, and the montana species is in the first group.
Group one of the Clematis species, which includes the montana version, flower very early in the growing season, generally in April or May. These plants produce flowers from the previous year’s growth since the stems don’t start growing until the summer. Therefore, Clematis montana needs a full year to flower from new growth. This early flowering from last year’s growth requires a particular method and timing for pruning to ensure that you don’t ruin this year’s bloom. Other species are pruned at the time montana is blooming.
Because of the early blooming season of Clematis montana, the best time to prune is as soon as possible after the bloom is complete. This ensures that you get to enjoy the full richness of the flowers, but that you won’t interfere with the new growth that will sprout next year’s bounty. Do not prune any later than midsummer, or about late July. Pruning too late will encourage new growth that will not get the chance to mature before the winter cold and will die off and be unable to produce new blooms next spring.
Carefully make cuts with pruning shears or sharp pruning scissors. The vinelike design of the Clematis montana will often result in twining and twisting. Make sure you cut carefully to avoid snipping areas you don’t want to cut back. Cut away any dead or damaged areas, as well as any vines that are running wild or ruining your intended look for the plant. While you prune, you can train some of the vines to grow in a desired direction by staking them facing a certain way. Remove any shoots on which the blooms are already starting to fade.
You do not have to prune Clematis montana at all if you don’t want to. Many gardeners grow this vinelike flower variety as a ground cover or to hide unsightly areas of the garden such as protruding tree roots or exposed bases of other plants. If your Clematis montana looks straggly or is not producing to its full potential, you can cut this plant back hard to as short as 4 to 6 inches to encourage fresh new growth. It may take a year or two for the flowers to return, but the plant will be healthier.