Knockout roses are cold-hardy, disease-resistant hybrids created by longtime rose developer William Radler. He developed this particular rose in 1988. and it had won the All-American Rose Award by the year 2000. This new hybrid became the fastest-selling new rose of all time. The knockout rose requires little care, which is one of its most attractive qualities. The best time to divide these roses is after the blooms and leaves have fallen off, in the fall.
Use your shovel to dig up a young knockout rose bush. Older bushes are more difficult to divide. Dig a bit farther out than you suspect the roots end, so as not to damage them.
Cut, with a garden handsaw, from a point between the trunks of the bush straight down through the roots. Divide the two halves of the bush.
Dig a second hole in the location you would like the new plant. Use the old hole for the other half of the rose bush. The holes must be twice as deep as the rose root ball.
Pour into each of the holes a mixture of compost, a teaspoon of rose fertilizer and additional garden soil. The new mixture should allow the rose bush stem and roots to be level with the top of the ground, at the same level they were on original, undivided plant.
Lower each of the knockout rose bush halves into its own hole. Push additional garden soil into each hole, pressing gently with your fingers until the bush is securely supported.
Cover the ground under the bush with mulch. This will protect the tender roots from the winter cold. If the winter is dry, water the bush occasionally, or whenever the soil feels dry about an inch from the surface. If you cannot easily check with your finger, use a trowel (small shovel) to dig down. The time rate of winter watering will depend on the precipitation in your location.