Knock out roses at hard landscape roses and can be pruned in late winter or early spring. If they need summer trimming this will not harm them at all. You can prune back wayward branches any time of year but heavy pruning is best done during the dormant season or in early spring. That said, if you live in a mild winter area you can also prune hardy roses in the fall and they will not suffer winter damage. Keep growing, Marianne Binetti