Knock Out rose
Rosa 'Radrazz'
Knock Out rose (Rosa 'Radrazz') is a shrub suited to the Colorado Front Range. It matures to about 3–4 ft tall and 3–4 ft wide, fast-growing, needs low to medium water, and prefers full sun to partial shade. The reliable landscape rose: reblooming cherry-red single flowers from spring to frost, and the best blackspot resistance of any common rose. Nearly care-free.
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At a glance
- Botanical name
- Rosa 'Radrazz'
- Variety / cultivar
- Knock Out
- Type
- Shrub
- Mature size
- 3–4 ft tall and 3–4 ft wide
- Planting spacing
- ~4 ft apart (3 ft for a hedge/screen)
- Hedge use
- Informal hedge or screen
- Bloom length
- Reblooms
- Hardiness zones
- USDA 5–9
- Growth rate
- Fast
- Water needs
- low to medium water
- Sun
- Best in full sun; tolerates partial shade.
- Colorado native
- No
- Foliage
- Deciduous
- Soil
- clay, loam, sandy
- Soil pH
- 6.0–7.5
- Hail tolerance
- moderate
- Wind tolerance
- moderate
- Salt tolerance
- low
- Bloom color
- red
- Bloom time
- early summer, mid summer, late summer, early fall
- Pollinator value
- moderate
Things to know before you plant
- ThornyIt is thorny, so site it away from paths, seating, and play areas.
Wildlife & ecology
- Pollinator value
- moderate
- Deer
- Not deer-resistant
Common problems on the Front Range
- Aphids
- Blackspot and powdery mildew
- Japanese beetle
These are general tendencies for this group of plants on the Front Range, not a diagnosis. Many are stress-driven and preventable with good siting and watering. For a specific plant or an active problem, consult a certified arborist or your local CSU Extension office.
Planting & establishment
Give it deep, regular water the first two seasons and steady moisture after; mulch to keep the roots cool and moist.
- Pruning: moderate.
Frequently asked questions
- Is Knock Out rose good for the Colorado Front Range?
- Yes, Knock Out rose is a well-suited shrub for Colorado's Front Range.
- What should I know before planting Knock Out rose?
- The main things to know: It is thorny, so site it away from paths, seating, and play areas.
- How big does Knock Out rose get?
- It matures to about 3–4 ft tall and 3–4 ft wide.
- How far apart do I plant Knock Out rose?
- Space Knock Out rose about 4 ft apart for a full, natural form, or about 3 ft apart for a faster hedge or screen.
- Is Knock Out rose hardy on the Front Range?
- Knock Out rose is hardy in USDA 5–9. The Colorado Front Range spans roughly USDA 4b–6a, so it is at its cold edge here. Site it in a warm microclimate and protect young plants.
- How much water does Knock Out rose need?
- It needs low to medium water once established.
- How fast does Knock Out rose grow?
- Knock Out rose is a fast-growing shrub. Growth rate depends on water and site conditions on the Front Range.
- Is Knock Out rose native to Colorado?
- No. It is not a Colorado native, but it grows well on the Front Range.
- Is Knock Out rose deer-resistant?
- No. Knock Out rose is not considered deer-resistant and may need protection where deer browse.
- Is Knock Out rose prone to pests or disease on the Front Range?
- Knock Out rose can be affected by aphids and other issues common to this group on the Front Range. These are general tendencies, not a diagnosis, many are stress-driven and preventable with good siting and watering. For a specific plant or an active problem, consult a certified arborist or CSU Extension.
- Is Knock Out rose a good hedge plant?
- Yes, as an informal hedge. Knock Out rose works best as a relaxed hedge or screen kept to its natural form rather than sheared into a tight box.
- How long does Knock Out rose bloom?
- Knock Out rose reblooms through the season, especially if you deadhead spent flowers on the Front Range. Bloom timing shifts a week or two with elevation and spring weather.
