Developed by Wisconsin rose breeder, William Radler, Knock Out roses hit the market in 2000 and quickly became one of the most popular roses in North America. Gardeners love these disease-resistant and drought-tolerant shrub roses because they bloom profusely with only minimal care. Blooming once every five to six weeks until frost, Knock Out shrub roses produce clusters of 3-inch, cherry red or pink blossoms that emit a slight fragrance, similar to that of tea roses. The widely adaptable Knock Out rose is hardy through zone 5, requires no deadheading and once established, needs only basic care to grow, thrive and flower.
Plant Knock Out shrub roses during mid-spring, after the soil is workable, in a location that has well-drained, moist, fertile soil and receives at least six to eight hours of sunlight each day. Space the shrubs at least 3 to 5 feet apart.
Spread a 3-inch layer of organic mulch around Knock Out shrub roses to insulate the soil, prevent the growth of competitive weeds and conserve moisture. Start the mulch at least 3 inches from the shrub's crown to allow vital air circulation.
Water once every five days during the first season of growth to help establish the root system. Reduce the frequency of watering thereafter to once every 7 to 10 days, allowing the soil to dry slightly between applications. Soak the soil to a depth of at least 6 inches at each watering to ensure the roots receive adequate moisture.
Feed Knock Out shrub roses once every month during spring, summer and fall, using a balanced 10-10-10 NPK fertilizer. Water lightly both before and after fertilizing to release the nutrients into the soil and prevent root injury. Check the dosage directions provided by the manufacturer for the best results.
Prune your roses during late winter, just before active growth resumes in spring, to keep the shrub healthy, visually appealing and growing in a compact manner. Use hedge clippers to cut back any overgrown branches and remove any diseased or damaged limbs and foliage.