Answer: It is a little bit difficult to give specific pruning advice without knowing what kind of shrub rose you have. The time to prune most landscape shrub roses (such as Knockout or the Carefree roses) is in late winter to early spring. Cut them back to about eighteen inches tall. You can also remove some of the oldest canes by cutting them at the base. This will help encourage vigorous new growth from the base and also help thin the bush so air and light can reach the center.
If you have a rugosa rose or a once blooming shrub rose, you would prune out about a third of the oldest canes each year, again cutting them off at the base in late winter or early spring. Then after right after it blooms, selectively prune out some of the longer canes to help control the size.
It may be that the variety you are growing naturally grows to a size too large for where it is planted. If that is the case, you may need to replace it with something that matures to a smaller size. I hope this helps.
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