Can I prune my double knock out roses now?

danain(z5 IN)August 28, 2007

My double knock out roses have been eaten badly by Japanese beetles. I can see new growth coming in on them and would like to cut out all the chewed up sections. Can I do this now or should I do it in the Fall or not at all?? My neighbor said to cut them down to about 6 inches in December but I don't know if that's right either??

What would you do?


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hostared(Z5, IL)

Knock Out Roses are easy.
Trim back so it looks shapely and they will recover and provide you with new growth.

I would not cut them down to 6" in December. I would wait till spring when you see new growth to cut out any dead wood.

    Bookmark   August 28, 2007 at 9:11AM
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I wouldn't do any heavy pruning this time of year in zone 5.

I also would avoid such pruning in December, unless the goal is to fit the plant under one of those protective caps.

How did the double Knock Out perform for you this year, aside from being a meal for Japanese beetles?

    Bookmark   August 28, 2007 at 9:33AM
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This is my first year growing KO's so take this with a grain of salt:) When I planted my three knockout roses earlier in the year I put one in a half barrel. I don't know if the soil was just not good enough or if putting it in the hottest part of the yard was too much or what but it looked awful. It was trying to die with major discoloration of the leaves. So I moved it and after doing so of course there more yellow and shriveled leaves. I just kept pinching them back to help the plant recover and now it is flowering and looks happy.

Seems like Knockouts are just so tough that by gently removing damaged foliages you cannot go wrong. Are we talking about the canes also? To be removed I mean. I think you are safe taking anything off that is damaged or dead.


    Bookmark   August 28, 2007 at 10:03AM
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You can take off the dead leaves, but don't do any real pruning right now. If you leave the canes alone they'll grow new leaves to replace the eaten ones. Don't prune it down before spring. In the spring you'll cut out the parts that were killed during the winter.

    Bookmark   August 28, 2007 at 10:55AM
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mxk3(Zone 6 SE MI)

Agree with above - light pruning/shaping is fine, save the heavy pruning for the spring (NOT December!).

Eric: I've had Blushing KO for three years now, and they are great performers! No, not the most exciting rose form nor exquisite fragrance (but the Blushing has a light, fruity scent nonetheless), but they do pump out the flowers and since they grow well in partial shade they give a nice shot of color in part-shade areas. Japanese beetles don't really bother mine, I'll occasionally find one on a flower, but since I have rugosas - they make a beeline right on over to those and disregard the KOs. Also, KOs really *ARE* resistant to blackspot - that in and of itself is reason to grow these great landscape roses! I don't have the Double KO, so can't offer any experience on that one.

    Bookmark   August 28, 2007 at 12:01PM
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i know everyone recommends not *cutting back* until spring ... but i am curious what the reason for that is?

    Bookmark   August 28, 2007 at 12:03PM
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With any pruning or cutting back, it usually puts out new growth, and this growth won't have time to sufficiently harden before winter. So I wait til spring, also, to do major cutting back. Same reasons for not fertilizing past August 1, in my zone 5 anyways. Except for Astilbes.

    Bookmark   August 28, 2007 at 12:16PM
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danain(z5 IN)

Look at these poor things! You can see at the bottom there is some new growth (the rusty color...the red is just the tag). After seeing how bad they look (I have 6)do you still think I should wait until Spring?

Thank you!

    Bookmark   August 28, 2007 at 12:25PM
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danain(z5 IN)

Forgot to tell you that this landscape was just finished in June. They all did great in the beginning before the beetles came.


    Bookmark   August 28, 2007 at 12:26PM
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Yes, even looking that bad I would leave it alone. What happens if you prune it down now is that it will stimulate the plant to start growing. The new growth will be very tender when the frost hits, and can weaken the whole plant and possibly even kill it over the winter. Oh, and any leaf that is still green (no matter how lacy it looks) is still helping the plant and making food. I have roses that look like this too, and one that looks even worse, and I'm just leaving them alone. I'm more worried about getting them through the winter than what they look like right now.

    Bookmark   August 28, 2007 at 1:02PM
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danain(z5 IN)

Okay, I'll leave them alone for now. Thank you!

How much do you think I should cut back in the Spring? And when in the Spring? I'm new at this.


    Bookmark   August 28, 2007 at 1:23PM
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prairiemoon2 z6 MA

I have had a Knock Out Rose for two years. It has been a great performer for me. Last year it was the last thing blooming in my yard. The foliage stayed pristine all season. The foliage stayed clean this year too with the exception of the spring winter moth caterpillars. They dropped down from the trees and made a mess of many shrubs including this one. But once they were history, I trimmed and pruned off the ugly foliage and it grew back beautiful healthy foliage that is still looking great. Japanese Beetles are not one of the pests I normally see many of for some reason.

Sitting in almost full sun, fertilized with only compost tea once this season and should have been more.

I agree that you can pull off the ugly foliage if it doesn't represent more than 1/4 to a 1/3 of the total. I also wouldn't recommend cutting the canes now. In the spring before the new growth starts showing. Here that would be March. How much to cut back, I leave for someone with more expertise to answer. I have only had roses in the yard two years. [g]

    Bookmark   August 28, 2007 at 4:11PM
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I haven't had roses long either, but I think it is fairly easy to see where to prune in the spring. Wait to do it after your last frost which should be around March or April. It is a signal for your rose to start growing again so wait until you are sure it is safe.

Now, when you look at your rose this spring you will see brown ends on the canes. That is dead wood, and you will cut all of that out. Make your first cut just below the brown wood into the green part of the cane. If you don't see any green cane then prune down to the soil. If the green cane is all white inside like an apple, it is good wood. If the inside is brown then you need to prune further down. Watch for dark areas on the green canes. That is canker and you need to prune below any canker you see. Once you have finished pruning seal all the cuts with something. I use regular white glue, but you can use carpenter's glue or nail polish. That will keep out borers which would otherwise lay their eggs inside the cut end of the cane.

Feel free to stop by the rose forum for more advice. I post there quite often and everyone is very helpful.

    Bookmark   August 28, 2007 at 4:38PM
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The other problem with cutting back in fall (it works fine in California and Texas) is that the cut ends don't heal (callus over) before freezing weather and then the cold travels down the cane and kills it. And I know that a lot of people recommend cutting back in fall but it's a terrible idea and is responsible for a lot of dead roses.
In spring, wait until the forsythia blooms or the rose just begins to put out new growth. Then you can see what is dead and cut that out.

    Bookmark   August 28, 2007 at 5:47PM
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danain(z5 IN)

Thank you for all the great advice. I will save this thread and I'll also visit the rose forum this Spring.


    Bookmark   August 29, 2007 at 8:34AM
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I've had seven knockouts for four years now. While I agree that heavy pruning should be saved for spring, you can certainly give the shrub a light pruning now to clean off some of the dead leaves. Like you, my knockouts get ataacked badly by japanese beetles beginning in June. Occasionally, I will spray them with Sevin when I can't stand it anymore. This will control the beetles for a short time, but they usually return until the end of August. However, it has been my experience that knockouts will bloom at least until mid October in my zone so don't give up on them for this season yet. They provide wonderful fall color. The beetles will leave and your roses should bloom again by mid September. I have also begun to prune them severly in spring to control their size and they seem to bounce back nicely. The ones in full sun have reached in excess of five feet and nearly as wide while the roses in partial shade have remained somewhat smaller and more manageable.

    Bookmark   August 29, 2007 at 10:06PM
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