Knockout rose shrubs are extremely low maintenance and easy to grow. They blossom approximately every five to six weeks during the growing season (until the first hard frost). Growing roses couldn't get any easier; in fact they do not even require dead-heading. They are hardy to zone 5. If left un-pruned the knockout rose shrub can reach a height of three to four feet and a spread of three to four feet. You can keep them trimmed down to create a shrub of a smaller height and width if that is what you desire. They will need to be pruned once a year in late winter or early spring.
Remove any dead, diseased, or damaged branches by cutting them off from the cane from which they are growing from. This should always be done immediately. Remember--do not place any diseased plant material in your compost bin.
Prune the Knockout rose shrub during the dormant season--late winter or early spring. Cut down the shrub by one-third. This will produce vigorous flowering during the summer months.
Remove several of the oldest canes each year. Cut them out at the base of the shrub. (Do this only if your plant is producing new growth from its base.) This should be done in late winter or early spring.
Trim to shape the rose shrub after the first flush of flowers. Snip off any undesired growth in order to define its shape. Trimming is a personal preference and does not have to be done.