Photo by Melody

PlantFiles: Shrub Rose
Rosa 'Rainbow Knock Out'

Family: Rosaceae (ro-ZAY-see-ee) (Info)
Genus: Rosa (RO-zuh) (Info)
Cultivar: Rainbow Knock Out
Additional cultivar information: (aka Rainbow Knock Out, RADcor)
Hybridized by Radler; Year of Registration or Introduction: 2007

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3 vendors have this plant for sale.

7 members have or want this plant for trade.


24-36 in. (60-90 cm)

24-36 in. (60-90 cm)

USDA Zone 4a: to -34.4 C (-30 F)
USDA Zone 4b: to -31.6 C (-25 F)
USDA Zone 5a: to -28.8 C (-20 F)
USDA Zone 5b: to -26.1 C (-15 F)
USDA Zone 6a: to -23.3 C (-10 F)
USDA Zone 6b: to -20.5 C (-5 F)
USDA Zone 7a: to -17.7 C (0 F)
USDA Zone 7b: to -14.9 C (5 F)
USDA Zone 8a: to -12.2 C (10 F)
USDA Zone 8b: to -9.4 C (15 F)
USDA Zone 9a: to -6.6 C (20 F)
USDA Zone 9b: to -3.8 C (25 F)

Bloom Color:
Apricot and apricot blend (ab)
Light pink (lp)

Bloom Shape:

Flower Fragrance:
No fragrance

Bloom Time:
Late Spring/Early Summer
Mid Summer
Late Summer/Early Fall
Mid Fall
Blooms repeatedly


Patent Information:

Other Details:
Resistant to black spot
Resistant to rust
Sets hips

Pruning Instructions:
Blooms on new wood; prune early to promote new growth

Soil pH requirements:
5.6 to 6.0 (acidic)
6.1 to 6.5 (mildly acidic)

Propagation Methods:
From softwood cuttings
From semi-hardwood cuttings
From hardwood cuttings
By grafting
By budding

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Thumbnail #1 of Rosa  by Calif_Sue

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By Calif_Sue
Thumbnail #3 of Rosa  by Calif_Sue

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There are a total of 9 photos.
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2 positives
4 neutrals
2 negatives

Gardeners' Notes:

Neutral DaylilySLP On Mar 5, 2015, DaylilySLP from Dearborn Heights, MI (Zone 6a) wrote:


Negative ckelisna On Oct 13, 2014, ckelisna from Tega Cay, SC wrote:

I've had them one year. I was attracted by the color of blooms but they stay small and don't last, leaving it looking unkempt. It's not nearly as big as other knockouts. I had to spray several times for aphids. I was counting on it growing without a lot of attention. Some stems had fungus and it was hard to shape. Many small branches developed tightly.

Neutral coriaceous On Feb 17, 2014, coriaceous from ROSLINDALE, MA wrote:

Rainbow Knockout sheds its petals cleanly, but as the season progresses it builds up a surface layer of blackened sepals/spent flowers that makes the shrub look unkempt and distracts my eyes from the new flowers. Other Knockouts cover these with new growth, but Rainbow Knockout does not.

I suppose you could use hedge trimmers to take off the spent blooms, but that doesn't seem to be something most people are inclined to do. Or you could deadhead, but Knockouts were bred to be "no-deadheading-needed" roses.

Unlike other Knockouts, Rainbow Knockout produces a lot of dense thorny twiggy growth with interspersed winter dieback that's tedious to prune by conventional rose-pruning techniques. A hedge trimmer would be useful for spring pruning.

In other respects, Rainbow Knockout is a good landscape plant---vigorous, floriferous, and highly blackspot-resistant. I haven't seen powdery mildew on them in my area.

I don't recall seeing them produce hips, either.

Update Dec. 2014: Radler's 2015 release, "The Peachy Keen" rose ('RADgor'), has similar colors, and I suspect may replace "Rainbow Knockout" ('RADcor') in the marketplace if it's an improvement.

Neutral paddleaddict On Apr 20, 2012, paddleaddict from Chesapeake, VA wrote:

There are 14 rainbow knock-out roses lining the front of my southwest facing beds that stay covered with powdery mildew from early spring to first frost. I live in zone 8. They receive no overhead irrigation and are growing in full sun conditions. They have excellent air movement and only late afternoon shade. Other knock-outs nearby are stellar. The rainbows have been established now for about 8 years, and receive routine maintenance. Both my husband and I are professionals in horticulture, but cannot get any solid reasons for their continuing condition. We have 'many' other varieties of roses throughout our yard that are amazing. The rainbows flower wonderfully, but like I said are plagued with powdery mildew. We are not eager to nuke them as we've created a song bird 'sanctuary' and hope to keep it pristine. Any ideas?

Positive Sandwichkatexan On Apr 1, 2012, Sandwichkatexan from Copperas Cove, TX wrote:

I have these planted in heavy shade and they still bloom like crazy . In my area they have no blackspot or mildew and they have beautiful hips in the winter . One of the few roses that will heavily bloom in shade .

Positive dovey On Oct 29, 2008, dovey from Columbus, OH (Zone 5b) wrote:

I like Rainbow Knockout, of all the knockout roses it's the prettiest. It makes a great choice for a tree rose.
It seems to enjoy a dryer climate over an area with high humidity.

Negative jetgirl On Jun 2, 2008, jetgirl from Alexandria, VA wrote:

I saw the Rainbow Knock Out rose at a nursery today, and the plants had significant MILDEW on the new growth (top 6", leaves and buds). The nursery is on a ridge with good air movement and all day sun. I think the supplier was Star Roses.

Neutral mystic On Feb 9, 2007, mystic from Ewing, KY (Zone 6a) wrote:

2007 AARS (All-American Rose Selection) winner.


This plant has been said to grow in the following regions:

Williford, Arkansas
Forest Falls, California
San Jose, California
Baton Rouge, Louisiana
Roslindale, Massachusetts
Minneapolis, Minnesota
Southold, New York
Concord, North Carolina
Columbus, Ohio
Fort Mill, South Carolina
Knoxville, Tennessee
Copperas Cove, Texas
Richmond, Texas
Alexandria, Virginia

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