Answer: How much to prune depends on what kind of rose you are growing. Roses are pruned in the spring, but some (hybrid tea roses) are pruned before they bloom, and some (old garden roses) are pruned after they bloom.
The hybrid tea roses need special winter protection in your area to survive the winter. These are sometimes cut back somewhat in the fall so they will fit inside rose cones or other protective devices. In the spring, they are pruned again to remove any winter damaged canes, thin the plant and to direct the new growth.
If you are growing your roses for competition, you would prune the plant quite hard. This results in fewer but larger blooms. Most home gardeners prefer to have the most blooms as possible so do not need to cut the plant down as much. Typically your height would be in the 12 to 18 inch range on a hybrid tea, assuming you do not have to remove more than that because of winter damage.
Hybrid tea roses are pruned in the spring as the buds begin to swell and you can tell which canes are alive and which have been damaged by the winter. I hope this answers your question.
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