Culture
Best grown in medium moisture, slightly acidic, well-drained garden loams in full sun to part shade. Best flowering and disease resistance generally occur in full sun, however. Water deeply and regularly (mornings are best). Avoid overhead watering. Good air circulation promotes vigorous and healthy growth and helps control foliar diseases. Summer mulch helps retain moisture, keeps roots cool and discourages weeds. Remove spent flowers to encourage rebloom. Crowns need winter protection in cold winter areas such as St. Louis. Remove and destroy diseased leaves from plants, as practicable, and clean up and destroy dead leaves from the ground around the plants both during the growing season and as part of a thorough cleanup during winter (dormant season). Prune as needed in late winter to early spring.
RAINBOW KNOCK OUT plants are self-cleaning (do not require deadheading of spent blooms).
Noteworthy Characteristics
Rosa is a genus of about 150 species of deciduous (occasionally evergreen) shrubs and climbers noted for their beautiful, often fragrant, single, semidouble or double flowers which are borne singly or in clusters on often prickly stems clad with 5-9 leaflets often having toothed margins.
Shrub roses are usually large-growing bushes between 4-10 feet tall and as wide. They are a very diverse group of hybrids and usually produce clusters of flowers several times a year but some may bloom just once in spring. They do not require the heavy pruning required of hybrid tea, floribunda and grandiflora roses unless being pruned to control size. Plants can be allowed to grow large with minimal pruning.
Genus name comes from the Latin name for rose.
RAINBOW KNOCK OUT is a compact mounding shrub rose that typically grows to 3-4’ tall and as wide. It is particularly noted for its ability to bloom in as little as 3 hours per day of direct sun with excellent disease resistance. Parents are 'RADtee' (female/seed) and 'RADral' (male/pollen). Single, 5-petaled, coral pink roses (to 2” diameter) with yellow centers bloom in clusters from May to frost. Flowers have no fragrance. Flowers are followed by orange-red hips. Foliage is satiny dark green throughout the growing season, but acquires some nice burgundy tones in fall. U.S. Plant Patent PP15,070 was issued on August 3, 2004. AARS award winner in 2007.
Problems
Roses are susceptible to a large number of diseases, the most common of which are black spot, powdery mildew, rust and rose rosette. Although good cultural practices are the first line of defense in disease control, regular preventative fungicide applications throughout the growing season are usually required, particularly in humid climates with regular rainfall such as the St. Louis area. Potential insect problems include aphids, beetles, borers, scale, thrips, rose midges, leafhoppers and spider mites. Local rose associations and extension services are usually able to offer specific recommendations and advice for selecting and growing roses.
RAINBOW KNOCK OUT has excellent resistance to the aforementioned diseases, and in particular to black spot and rust, and often does not need regular fungicide treatments.
Uses
Grow as a specimen or in small groups in borders, cottage gardens, foundations or rose gardens. Also effective as a hedge.
Excellent selection for part shade locations.