Knock Out roses, rose cultivars valued for their low maintenance and disease resistance, reach about 6 feet in height and width, though pruning yields a denser growth habit. Hardy in zones 5b through 9, the plants thrive throughout much of the United States with little care. With regular upkeep, Knock Out roses produce successive flushes of blossoms during spring, summer and fall months. The cherry-red flowers require no deadheading because of their self-cleaning properties. Common throughout the United States, Knock Out roses attract beneficial insects and add interest to any landscape.
Plant Knock Out roses during spring, after the threat of freezing passes, in a location that receives full sunlight and consists of well-drained, moist soil. Plant Knock Out roses in soil with a pH level between 6.0 and 6.5 for best results. Space the Knock Out rose plants 3 to 4 feet apart.
Spread a 3-inch layer of organic mulch over the planting site to help conserve water, reduce weed growth and add nutrients to the soil. Prevent the mulch from touching the base of the plant, which could cause rotting or disease.
Water Knock Out roses once a week or when the soil feels dry to a depth of 1 inch. Pour the water directly over the roots to conserve water and minimize the chance of fungal diseases. Never allow standing water to accumulate around the plant's roots.
Feed the roses once a month during spring and summer to provide adequate nutrition for rapid growth and consistent blooming. Water lightly before feeding to avoid causing root burn. Apply a 20-20-20 NPK fertilizer following the directions on the package for the best results.
Remove dead, diseased and damaged branches with pruning shears throughout the year. Cut back any excessively long growth to improve the plant's appearance and promote a bushy habit.