Shrub rose (Rosa 'Radrazz' KNOCK OUT)
The resilient Rosa 'Radrazz' KNOCK OUT Shrub rose offers stunning, continuous cherry-red blooms from June to frost with high disease resistance.
Scroll down to discover growing tips, care requirements, companion plants, and more
Complete Plant Information
Overview
The Rosa ‘Radrazz’ KNOCK OUT, classified generally as a Shrub rose, is celebrated for its exceptional vigor and continuous bloom cycle, making it a reliable staple in modern landscapes. This particular cultivar sets itself apart by delivering masses of cherry-red flowers consistently from early summer until the first hard frost. Its primary value lies in its low-maintenance profile combined with striking visual appeal.
As a compact deciduous shrub, the Rosa ‘Radrazz’ KNOCK OUT typically remains between 3 and 4 feet tall and wide, fitting neatly into various garden designs without demanding the extensive pruning often associated with traditional roses. This Shrub rose provides excellent foundational color and structure, thriving even in locations that receive only partial sunlight.
Gardeners especially appreciate the robust nature of the KNOCK OUT family, which exhibits superior resistance to common rose ailments like black spot and mildew. This disease resistance minimizes the need for frequent chemical applications, allowing the gardener to enjoy the vibrant display of the Rosa ‘Radrazz’ KNOCK OUT naturally.
Fast Facts
- Plant Family: Rosaceae
- Plant Type: Deciduous shrub
- Hardiness Zones: USDA Zones 5-9
- Size at Maturity:
- Height: 3-4 ft
- Spread: 3-4 ft
- Bloom Time: June to frost
- Bloom Description: Cherry red
- Sun Exposure: Full sun to part shade
- Water Needs: Medium
- Maintenance Level: Medium
How to Grow
For optimal performance, plant this Shrub rose in medium moisture, slightly acidic, well-drained garden loams. While Rosa ‘Radrazz’ KNOCK OUT exhibits excellent disease resistance even in part shade, achieving the best flowering and the highest level of disease management occurs when the plant receives full sun. Plant in late winter or early spring if possible, ensuring good air circulation around the developing shrub.
Routine care centers on deep, regular watering, preferably done in the mornings to allow foliage to dry before nightfall; absolutely avoid overhead watering systems. Apply a summer mulch layer to help retain consistent soil moisture, keep the root zone cool, and suppress competitive weeds. Pruning is minimal, generally only required as needed in late winter or early spring to shape the plant or remove any dead wood.
To maximize rebloom throughout the summer season, remember to remove spent flowers consistently. In colder extensions of its hardiness range (such as Zone 5/St. Louis winters), providing winter protection for the crowns is recommended. Always clean up and destroy fallen leaves during the growing season and winter cleanup to minimize overwintering fungal spores.
Landscape Uses
The versatility of the Rosa ‘Radrazz’ KNOCK OUT Shrub rose means it performs beautifully in numerous landscape settings. Its uniform, compact size makes it an outstanding choice for mass plantings where hedging is desired, providing a dense, colorful barrier early in the season. It excels when used as an accent plant or specimen in cottage gardens or foundation plantings where its high visibility is appreciated.
Consider planting Rosa ‘Radrazz’ KNOCK OUT alongside complementary perennials that prefer similar medium water needs, such as Salvias or ornamental grasses, to create textural contrast against its dark purplish-green foliage. Its deep cherry-red flowers stand out well against lighter-colored hardscaping or foundations. Because the KNOCK OUT rose is noted for thriving in light conditions, it is also an excellent, robust inclusion in partially shaded borders where other sunny roses struggle.
Standout Features
Flower Qualities
- Showy
- Fragrant
Fruit Qualities
- Showy
Noteworthy Characteristics
Rosa ‘Radrazz’ KNOCK OUT is a compact shrub rose, setting itself apart by needing as little as 3 hours of sun daily while maintaining superb disease resistance. It produces single, lightly fragrant, cherry-red roses up to 3.5 inches wide in clusters that persist from May well into frost. Following its long blooming season, attractive orange-red hips develop, and its dark summer foliage transitions to purple and burgundy tones in the fall.
Tolerances
- Air Pollution
Potential Problems
While general rose culture involves vigilance against common issues like black spot, powdery mildew, and rust, the primary strength of the Rosa ‘Radrazz’ KNOCK OUT is its high resistance to these very diseases. This means preventative fungicide treatments are often unnecessary, reducing maintenance workload significantly.
Should insect pests like aphids, scale, or spider mites appear, good cultural practices remain the first defense. Ensuring proper watering techniques (deeply, not overhead) and maintaining strong air circulation helps keep the Shrub rose vigorous. If serious infestations occur, local extension services can provide targeted advice, though frequent chemical intervention is rarely required for this particular cultivar.
Frequently Asked Questions
What hardiness zones is Shrub rose suitable for?
This robust Shrub rose, Rosa ‘Radrazz’ KNOCK OUT, is suitable for USDA Hardiness Zones 5 through 9.
How large does Rosa ‘Radrazz’ KNOCK OUT grow?
Rosa ‘Radrazz’ KNOCK OUT typically matures to a height between 3 and 4 feet, with a comparable spread of 3 to 4 feet.
When does Shrub rose bloom?
The bloom period for this variety is reliable, starting in June and continuing without pause until the first killing frost, featuring cherry-red flowers.
What sun exposure does Rosa ‘Radrazz’ KNOCK OUT need?
This versatile shrub rose thrives in conditions ranging from full sun (where flowering is maximized) to partial shade, requiring a minimum of 3 hours of direct sun per day.
Conclusion
The Rosa ‘Radrazz’ KNOCK OUT Shrub rose delivers unmatched modern performance through its continuous, vivid cherry-red flowers and outstanding disease resistance. This plant significantly lowers the typical rose care commitment while providing structure and season-long color ideal for hedges or specimen planting. Assess your site conditions to ensure compatibility with its USDA Zone 5-9 requirements before planning your planting this late winter or early spring.
Companion Planting
Selecting companions for the Rosa ‘Radrazz’ KNOCK OUT should focus on plants that share its preference for medium water use and well-drained soil, while potentially offering complementary heights or textures. Many drought-tolerant perennials, such as Russian Sage (Perovskia atriplicifolia) or various Catmints (Nepeta species), pair well, as they appreciate similar sun exposure and their grayer, airier foliage provides a soft contrast to the dark green rose leaves. Furthermore, since the Shrub rose resists many common foliar diseases, avoid neighboring plants that are highly susceptible to mildew, as diseases can sometimes jump across species boundaries under high humidity.
Seasonal Care Calendar
Late Winter/Early Spring is the prime time for structural pruning of the Rosa ‘Radrazz’ KNOCK OUT, focusing on removing thin or crossing branches to improve interior air flow. As days lengthen approaching the last frost date, apply a balanced slow-release fertilizer formulated for roses, followed by a fresh 2-3 inch layer of summer mulch, ensuring the base of the plant remains uncovered. Throughout the actively growing season, deadheading (removing spent blooms) is essential to signal the plant to produce more flowers rather than forming hips. In autumn, focus on thorough cleanup around the base of the plant, removing all fallen leaves to reduce disease inoculum carryover into the following year.
