The Knock Out rose is a hybrid rose bush created by rose breeder William Radler. The Knock Out rose requires little maintenance and tolerates colder temperature than many other varieties of roses. It also tolerates hot weather throughout the United States and experiences fewer instances of disease and pest attacks. With proper care, Knock Out roses will thrive in most gardens.
Knock Out roses tolerate dry conditions, but prefer moist, well-drained soil. These roses perform best in soil with a pH of 6.0 to 6.5. Use a home testing kit or take a sample of your soil to your local extension office to test for pH levels before planting Knock Out roses. If necessary, amend the soil with sulfur or pine needles to lower the pH, or with lime to increase the pH.
Knock Out roses require at least four hours of sunlight per day but prefer six to eight hours. Lack of sun may lead to reduced flowering.
Plant Knock Out roses between November and April, during their dormant period. Plant the bushes at least 3 feet apart, to allow for some air circulation between established plants. Add 2 to 3 inches of mulch around the base of Knock Out roses. This will help to keep soil moist as well as providing extra nutrients for the plant.
Keep the soil evenly moist. Newly planted Knock Out roses require regular watering until the plants become established.
Feed Knock Out roses once a month during the growing season with a 12-6-6 or 10-20-10 fertilizer for best results. Discontinue fertilizing Knock Out roses in late summer, to allow the plants to go into dormancy. Resume fertilization in the spring.
Knock Out roses are self-cleaning, so deadheading of flowers is not necessary. These roses require pruning at least once every three years. When not pruned, Knock Out roses grow at least 3 to 4 feet tall and 3 to 4 feet wide. A yearly pruning in late winter will keep the bush at a manageable size. Use sharp, sterilized pruning shears to cut back Knock Out roses. Prune back to 12 to 18 inches tall to encourage new growth in the spring.
Although winter hardy to USDA hardiness zone 5, consider protecting Knock Out roses during especially cold winter weather. Adding 6 to 8 inches of mulch around Knock Out roses after the plant has gone into dormancy will help to protect it in cold climates. Cover rose bushes with burlap for added protection.