Knockout Roses
Rosa 'Radrazz' (Knock Out series)
Quick Definition
Knockout roses are low-maintenance landscape roses that bloom continuously from spring through frost without deadheading. Disease-resistant, heat-tolerant, and available in red, pink, yellow, and white. Prune hard in late winter (February to March).
Quick Facts
- Type
- Landscape shrub rose
- Zones
- 5 to 10
- Sun
- Full sun (6+ hours)
- Height
- 3 to 4 ft (18 to 24 in for Petite)
- Bloom Period
- Spring through hard frost (continuous)
- Blooms On
- New wood (prune in late winter)
- Disease Resistance
- High (black spot, mildew resistant)
- Deadheading
- Not required (self-cleaning)
- Pruning
- Hard in late winter (Feb to March)
- Fertilizer
- Rose fertilizer 3 times per year
Why Knockout Roses Changed Everything
Before Knockout roses, roses were high-maintenance divas requiring constant spraying, pruning, and coddling. The Knock Out series (introduced in 2000 by Star Roses) changed that by breeding disease resistance, continuous blooming, and self-cleaning flowers into a compact, landscape-friendly shrub. They bloom from spring through hard frost without deadheading, resist black spot and powdery mildew, and tolerate heat, humidity, and neglect.
Knockout Rose Varieties
| Variety |
Color |
Height |
Flower Type |
| Original Knock Out |
Cherry red |
3 to 4 ft |
Single |
| Double Knock Out |
Red |
3 to 4 ft |
Double (fuller) |
| Pink Knock Out |
Pink |
3 to 4 ft |
Single |
| Sunny Knock Out |
Yellow fading to cream |
3 to 4 ft |
Single |
| White Knock Out |
White |
3 to 4 ft |
Single |
| Petite Knock Out |
Red |
18 to 24 in |
Single (dwarf) |
Regional Notes
Central Plains (Omaha):
Knockout roses thrive in Omaha's zone 5b climate. Prune hard in late March (after last hard freeze). Rose rosette disease is present in the area: inspect plants monthly for distorted growth and remove infected plants immediately. We recommend spacing 4 feet apart and avoiding monoculture plantings (mix with other shrubs to slow disease spread).
Frequently Asked Questions
When should I prune Knockout roses?
Late winter (February to March) before new growth starts. Cut the entire plant back to 12 to 18 inches above ground. This sounds dramatic but Knockout roses grow fast and bloom on new wood. Hard pruning produces a compact, floriferous plant. Plants pruned lightly become leggy and top-heavy within 2 to 3 years.
Why do my Knockout roses look terrible?
Three common causes: not pruned hard enough (leggy, sparse), rose rosette disease (witches' broom growth with red distorted leaves), or too much shade (need 6+ hours of sun). Rose rosette is fatal and the plant must be removed. Leggy plants recover with a hard late-winter pruning to 12 to 18 inches.
Do I need to deadhead Knockout roses?
No. Knockout roses are self-cleaning: spent flowers drop on their own and new buds form without intervention. Deadheading can speed up the next flush of bloom by a few days but it's not necessary. The whole point of Knockout roses is low maintenance.
How big do Knockout roses get?
Standard varieties reach 3 to 4 feet tall and wide if left unpruned. With annual hard pruning to 12 to 18 inches in late winter, they stay compact at 3 feet. Petite Knock Out stays 18 to 24 inches. Without pruning, they can reach 5 to 6 feet and become leggy and unattractive.
What is rose rosette disease?
A fatal viral disease spread by tiny eriophyid mites. Symptoms: excessive red thorny growth (witches' brooms), distorted leaves, and rapid decline. There is no cure. Remove and destroy infected plants immediately to prevent spread to nearby roses. Rose rosette has devastated Knockout rose plantings across the US since 2010.
