Climbing roses should be pruned for the same reasons you prune other roses: for plant vigor, for plant shape, and for abundant flower production, but they are pruned a bit differently than other roses. As with any other pruning, you will need sharp, clean pruners.
Climbing roses are generally broken down into two categories, once-blooming and repeat-blooming, but regardless of their type, they bloom mainly on lateral branches that come from the main canes. In order to encourage roses to put out more flowering laterals, train the canes as horizontally as possible. A trellis, fence, wires or an arbor is ideal. Remember that roses need good air circulation and if climbing on a wall, be sure to position the support at least 3 inches away from the surface.
When a climbing rose is first planted, it is best to let it to go unpruned for the first 2 or 3 years. Except for the removal of dead wood, do not prune anything. Let the rose develop long main canes. Then select 4-6 canes that are growing in the direction that you want them to grow, and prune out the rest all the way to the ground. This is best done in the late winter while the rose is still dormant. These strong canes should then be trained to fan out horizontally without crossing each other. They may be held in place with soft plant ties. The tips should grow more or less horizontally. The shoots that come from these canes are the flower producers.
Pruning Spring-Blooming Climbing Roses
This type of rose blooms only once per season and usually blooms on wood from the previous year. Prune these roses right after flowering if finished. If pruned late in the year, they may not bloom the next year. If the plant produced many canes, remove one or two of the oldest and the weakest to the bud union or ground. Retie the new canes horizontally to your fence, wire, trellis or arbor. Late winter pruning should only be done to remove dead wood, suckers, twiggy growth or hips. (You can often tell if a climber is once-blooming because many of the once-blooming roses have very flexible canes and small flowers borne in clusters.)
Pruning Repeat-Blooming Climbing Roses
Repeat-blooming climbers are pruned in late winter when the rest of the roses are pruned. Remove all suckers and twiggy growth. Cut all the flowering laterals that rise from the main canes back to 2 or 3 buds. Retie the canes in a horizontal position, if climbing on a fence or wall. On an arbor or gazebo, fan out the cans as much as possible. To encourage a repeat-blooming climber to repeat during the season, cut off the spent blooms to the five leaf
leaflet that has a good bud-eye. This bud-eye will yield the new growth that produces more blooms.
When the “scaffolding” becomes very old and “barky”, these canes tend to quit production and should be removed. Take out the oldest cane all the way to the ground and use another cane to replace it.