Pruning roses promotes air circulation, which helps keep the rose plant healthy. Shrub roses are apt to become tangled and overgrown; dense thickets can contract fungal or bacterial diseases. Prune rose shrubs each year in the spring to keep the plant healthy, promote new growth, remove old growth that won't flower and maintain the shape of your shrub rose. If your shrub rose grows unwieldy over the growing season, prune back long branches to a manageable length using anvil pruners.
Wait until frost danger passes for your area to prune your rose shrub. The University of Illinois advises waiting until forsythia blooms as a sign that it's time to prune. Inspect your rose shrub for dead, diseased or damaged canes. Dead canes are tan or brown in color. Diseased or damaged canes may have blotches or wounds or look shriveled.
Cut off dead, diseased or damaged canes using anvil pruners. In between each cut, spray your pruners with a disinfectant spray so you don't accidentally spread disease to healthy parts of the bush.
Clip off thin, weak shoots that are thinner in diameter than a pencil, since they won't support the weight of roses.
Perform no additional pruning if your shrub rose is less than three years old. Young shrub roses are still developing their shape and should be allowed to produce new growth. If your shrub rose is mature, proceed.
Prune away 1/3 of the old growth canes each year in the spring to promote new growth and prevent the shrub rose from becoming too dense. Leave green, new growth and remove thick woody canes. Shrub roses flower on mature wood but not old growth. In subsequent years, remove another 1/3 of the old growth wood and leave new wood so that the shrub rose always has both new and old wood.