Shrub Rose 'Rainbow Knock Out'

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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 n...Read Moreearly 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.

Rainbow Knockout sheds its petals cleanly, but as the season progresses it builds up a surface layer of blackened sepals/spent flowers th...Read Moreat 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.

Petals fade to near white before dropping. I find this is a distraction and looks bad.

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.

There are 14 rainbow knock-out roses lining the front of my southwest facing beds that stay covered with powdery mildew from early spring...Read More 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?