Many gardeners desiring a thriving shrub rose choose a Knock Out rose variety. Not only are these roses beautiful with their showy blossoms throughout the summer, but they are exceedingly easy to care for as well. With minimal maintenance, a Knock Out rose bush can easily grow to heights of up to 6 feet when it grows in a sunny area and receives regular fertilizer. Trim Knock Out rose bushes before the growing season begins to give your Knock Outs the best start to the growing season.
Examine the rose bush carefully, looking for dead canes and canes that cross or rub on each other. If you find dead canes, cut these canes off just above the crown of the bush. If you find crowded and rubbing canes, cut these canes back to the point where they intersect with a larger cane.
Find any canes with portions of unhealthy growth. If you cut through an unhealthy cane, you will find the center of the cane looks dull brown. Healthy canes look white on the inside. Remove any unhealthy portions of canes by cutting back these canes to the point just above where a healthy bud is growing. Make sure the inside of the cane looks white at this point to indicate a healthy portion of cane.
Cut back the oldest canes (canes that are over 3 years old--these canes will have the dull brown insides). Remove up to 1/3 of the entire number of canes on the bush by cutting them back at the crown of the plant. These canes crowd the rose bush and they do not produce significant blooms. Leave at least five viable canes as you remove the old canes.
Collect all the foliage you remove from the Knock Out bush in the bucket and discard the refuse in a compost bin or the garbage. Do not leave foliage littering the ground around the shrub because it can lead to disease.
Deadhead spent blossoms throughout the growing season. Clip the faded blooms approximately 3 inches below the blossom with the pruning shears. Discard the blossoms in a compost bin or the garbage.