Prune a rosebush in the summer by only trimming it lightly for shape, deadheading the faded blooms, and removing old or damaged wood. Prior to pruning, submerge the pruning shears in a bleach mixture made of one part bleach and 10 parts of water.
Avoid hard or heavy pruning during the summer. Water the roses thoroughly before pruning the bush to prevent damage due to stress. This also keeps the plant cool when pruning during the summer. After sanitizing the shears, snip off any faded flowers. Cut back any damaged wood or dead branches. When pruning, cut at a 45-degree angle just above the nearest stem. Remove awkward, rubbing branches. Snip away any suckers growing at the bottom of the rose plant to focus the plant's energy on flowering instead of growing.
Finish by trimming the bush for shape. Remove no more than one-third of the plant during this step. Carefully part the branches when selecting limbs to remove so that you do not accidentally injure the plant or break any of the limbs. Also, keep an eye out for diseases manifesting in leaves and branches with black spots or blotches.