How to Prune Climbing Roses
Prune climbing roses in late winter by keeping the main structural canes and cutting the flowering side shoots back to two or three buds. Train the main canes horizontally to maximize bloom.
Climbing roses flower on short side shoots (laterals) that grow off a permanent framework of long main canes. The pruning goal is to keep that framework and refresh the laterals.
In late winter, first remove any dead, damaged, or very old unproductive canes at the base. Then shorten each flowering side shoot back to two or three buds — this is where next season's blooms will come from. Finally, tie the main canes as close to horizontal as the support allows; horizontal canes flower along their entire length instead of only at the tips.
Rambling roses are different: they bloom once on old wood, so prune them right after flowering, not in late winter.