Knock Out was first introduced in 2000 and hailed a "breakthrough shrub rose" by the All-American Rose Selections because of its exceptional disease resistance and hardiness. It was one of three roses to win the prestigious AARS award for outstanding garden performance in 2000.
Knock Out Roses have been called the perfect landscape shrub and are virtually disease-free. During a 4 year research study at the Texas A&M University System Agricultural Research and Extension Center in Dallas, scientists found Knock Outs to be one of the finest landscape roses ever tested. During testing, no pesticides of any kind were ever applied.
"It has proven to be almost resistant to black spot, the fungal disease that is the scourge of roses across much of the United States," said Dr. Steve George, Texas Cooperative Extension horticulturist in Dallas. "It is also resistant to powdery mildew and aphids. It is cold-hardy throughout the state and will grow in a wide range of soils (even highly alkaline clays) and is very heat- and drought-tolerant once established."
These roses have changed the way many people view roses. Shrub roses, especially when compared with traditional varieties, are impressive for many reasons: their natural disease-resistance, their willingness to grow in a variety of climates with a minimum of attention from the gardener, their compact growth habit (very little pruning required), not to mention the great beauty of their flowers, which are borne consistently over a very long season.
Knock Out is a winner that will endear itself to gardeners eager for the beauty and versatility of rosebushes but unwilling to spend extra hours nurturing “marginal” plants. This compact, 3-foot by 3-foot shrub rose blooms constantly until hard frost with multiple bright cherry red flowers that require no deadheading. The large, shapely leaves are a burgundy-tinged deep green that darkens with cool weather. Orange rose hips arrive later, providing a final display. This plant is tough, crown-hardy to –20 degrees and resistant to black spot, the foliar scourge of roses.
When planting bare root Knock Out Roses in April, or from a container later on, make sure the graft union is planted 1 to 2 inches below soil level. This helps preserve its cold hardiness.
Broadcast a slow-release granular fertilizer, high in nitrogen but with little, if any, phosphorus and potassium. Knock Out Roses are quite drought-tolerant but should be watered amply its first year.
Mulch the planting area with several inches of shredded hardwood. This is visually appealing, conserves soil moisture, deters weeds and provides insulation against cold. Additional winter protection is not required.
When forsythia blooms the following April, prune any dead wood and fertilize again. In future years, if necessary, prune the shrub hard to the ground to maintain its compact form.
Knock Out Roses bloom continuously if the faded blooms are removed regularly. I visit mine every week and twist off the old buds. Every 4 weeks, I cut long stems back by half. This two-step process keeps new growth coming and removes the hormone-filled hips that tell the rose to bloom more slowly.
The Knock Out rose is a result of crossing a found rose seedling of Carefree Beauty and a floribunda seedling of Razzle Dazzle.
Even more floriferous and disease-resistant than its famous parent, Rainbow Knock Out is a bushy and compact landscape shrub rose with short stems bearing glossy, dark green leaves. Its blooms are single-form flowers that start out as pointed buds and appear abundantly throughout the growing season. The delicate five-petaled flowers are two inches in diameter and are a deep coral-pink color with a yellow center finishing nicely to light coral.
Rainbow Knock Out will have a nice display of blooms late into the season for a lovely fall bloom, and while it does not exhibit a strong fragrance, the petals emit a delicate sweetbriar scent. Suitable for container growing in small spaces, this rose is the prefect accent to any garden. It is also winter hardy to zone 4 and is fully resistant to black spot, mildew and rust.
Class: Landscape shrub rose
Plant Habit: Bushy compact round
Growth Habit: Very abundant and continuous, will bloom year round in mild climates
Stem Length: Short
Foliage Color: Dark green, semi-glossy
Disease Resistance: Fully resistant to black spot, powdery mildew and rust
Hardiness: Zone 5, Zone 4 with winter protection
Flower Color: Deep coral pink with yellow center finishing nicely to light coral
Bud Form: Pointed
Flower Form: Single
Flower Size: 2" diameter
Petal Count: Approx. 5
Fragrance: No flower fragrance, but the petiols emit the distinctive sweetbriar smell of the moss roses when slightly pressed
Parentage: RADtee x RADral
Hybridizer: William Radler
Introducer: The Conard Pyle Co.