In order to prune climbing roses, you will need the following: ties and pruning sheers. To maximize the impact of climbing roses you will need to evaluate the branching. Making sure that you allow the stem to be horizontal as much as possible will increase the number of blooms on a stem. Therefore, it may be necessary to unwind it and rewrap it around the post. Tie off the stem, as you bend it and wind it. Be careful to avoid overextending it. Pruning time is dependent upon your own microclimate in your area. There is no general time. Trim the stem where needed. When it blooms, you will need to clip back blooms in order to continue to force it to grow horizontally.