Rose Guide
How to Prune Grandiflora Roses
Prune grandifloras in late winter like hybrid teas but leave more height, since they grow tall. Keep four to six strong canes, shorten them by about a third, and remove weak and crossing wood.
Grandifloras combine hybrid-tea blooms with a taller, bushier habit, so they are pruned similarly but left larger. In late winter, remove all dead, weak, and crossing growth, keeping four to six of the strongest canes.
Shorten those canes by roughly a third rather than cutting them low, so the plant flowers along its considerable height instead of only at the top. Cut to outward-facing buds to keep the center open and airy, which helps prevent disease.