Ask a Question forum→I killed my unkillable knock out roses- help

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Name: DrAshish
Newtown, PA (Zone 6b)
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Drashish
Jun 2, 2020 9:02 PM CST
Help, I sprayed my 4 year old establish double knock out roses bushes with old 3:1 Bayer insecticide. Within days the new soft growth started to droop, now 1 week later it looks like all the Branches and leaves are dry and brittle. Each bush has 4-6 established canes. Can I salvage this? Do I prune down to the base canes in which I lose all red growth, all dying green leaves until I just have 6 sticks with thorns in the ground? I live in Philadelphia area so temperatures are starting to be summer like so everything I read online only refers to heavy pruning in early spring, not at this stage of "growth". Nothing to say about how ugly it will look this season if I do.
Thumb of 2020-06-03/Drashish/89ee14


Thumb of 2020-06-03/Drashish/14921c

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Name: Porkpal
Richmond, TX
Charter ATP Member Dog Lover Cat Lover Keeper of Poultry Keeps Horses I was one of the first 300 contributors to the plant database!
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porkpal
Jun 2, 2020 9:41 PM CST
Wash it off with a strong spray from the hose then wait to see how it does. Do nothing that might further stress the plant. I bet it will recover - roses are tough.
Porkpal
Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Jun 3, 2020 2:16 AM CST
I agree But as far as cutting then back, back, yes, you can do that, too. Just wait awhile. One summer my fairy roses were so infested with spider mites that in desperation, I cut them way back after repeated sprayings for the mites. Mind you, this was in July! They recovered quite nicely. Smiling
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Name: Sally
central Maryland
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sallyg
Jun 3, 2020 5:35 AM CST
Good luck!
Just sayin' .. I killed knock outs without using spray lol
i'm pretty OK today, how are you? ;^)
Name: stone
near Macon Georgia (USA) (Zone 8a)
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stone
Jun 3, 2020 10:10 AM CST
sallyg said:Good luck!
Just sayin' .. I killed knock outs without using spray lol


How?

Last winter, I cut a bunch of knockouts down almost to the ground... like the homeowner asked for...

Tossed the clippings in the back of my truck... set them out in the garden when I got home... most grew and are flowering... about all I did was water the cuttings (once)after sticking them in the sand.

Edit:
RE the roses in the pictures...
Have you been shearing those?
They look awful thick... I'd go in there and create some air flow By thinning branches... I suspect they got sick because of how they've been maintained.
having the growth that thick is bad for most plants.




[Last edited by stone - Jun 3, 2020 10:14 AM (+)]
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Name: one-eye-luke US.Vet.
Texas (Zone 8a)
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oneeyeluke
Jun 3, 2020 2:11 PM CST
Looks like Rose Rosette Disease (Witches' Broom Virus) to me. Before you sprayed what were your Knock outs doing? Research the disease RRD and you will see what I'm talking about. It wiped out every rose at our botanical garden leaving none.
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Name: Lynda Horn
Arkansas (Zone 7b)
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gardenfish
Jun 3, 2020 2:56 PM CST
Good suggestion. Thumbs up
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Mother Teresa
Name: Porkpal
Richmond, TX
Charter ATP Member Dog Lover Cat Lover Keeper of Poultry Keeps Horses I was one of the first 300 contributors to the plant database!
Garden Ideas: Level 2 Plant Identifier Raises cows Roses Farmer Celebrating Gardening: 2015
porkpal
Jun 3, 2020 2:57 PM CST
I don't think it is Rose Rosette. Do you have any earlier photos of that bush.
Porkpal
Name: Daisy I
Reno, Nv (Zone 6b)
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DaisyI
Jun 3, 2020 2:58 PM CST
I doubt Bayer 3:1 would do that unless you sprayed in the sun and heat of the day.
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Name: DrAshish
Newtown, PA (Zone 6b)
Don’t worry, be happy 😊
Drashish
Jun 3, 2020 7:44 PM CST
Thanks guys. I though of rosette virus disease but timing is too coincidental plus the spray also fell on some salvia Mays and they reacted the same way so had to be the spray. Plus before spray there was great fleshy soft red vine growth about 6-8 inches

Pruning and airing- I agree, I had a outside person prune this year since they got to thick and I was late and yes he didn't do a good job.

Washing off 2 weeks after spraying , uhm no sure but I did today, plus we got a drenching heavy rain storm after I washed this am too.

My real question is can I cut them down to 18 inches height above ground (meaning just the 6 main canes which are thorny and bare at that height? If so, how long can I see for green Leaves to sprout. It'll look ugly Since it's in front of the house but might be a fresh start in June. Just don't know how low can I cut a rose bush.

I can tell you they were beautiful last season and contrasted nicely
Against a white stone home.
If you fail, try and try again
Name: Daisy I
Reno, Nv (Zone 6b)
Not all who wander are lost
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DaisyI
Jun 3, 2020 9:24 PM CST
If you leave 3 leaf nodes on each cane, there will be more than enough left to regrow.
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and proclaiming...."WOW What a Ride!!" -Mark Frost

President: Orchid Society of Northern Nevada
Webmaster: osnnv.org
Name: Lynda Horn
Arkansas (Zone 7b)
Eat more tomatoes!
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gardenfish
Jun 4, 2020 2:08 AM CST
I agree go ahead, and good luck!
Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.
Mother Teresa
Name: DrAshish
Newtown, PA (Zone 6b)
Don’t worry, be happy 😊
Drashish
Jun 5, 2020 2:22 PM CST
Thanks guys. I though of rosette virus disease but timing is too coincidental plus the spray also fell on some salvia Mays and they reacted the same way so had to be the spray. Plus before spray there was great fleshy soft red vine growth about 6-8 inches

Pruning and airing- I agree, I had a outside person prune this year since they got to thick and I was late and yes he didn't do a good job.

Washing off 2 weeks after spraying , uhm no sure but I did today, plus we got a drenching heavy rain storm after I washed this am too.

My real question is can I cut them down to 18 inches height above ground (meaning just the 6 main canes which are thorny and bare at that height? If so, how long can I see for green Leaves to sprout. It'll look ugly Since it's in front of the house but might be a fresh start in June. Just don't know how low can I cut a rose bush.

I can tell you they were beautiful last season and contrasted nicely
Against a white stone home.
If you fail, try and try again
Name: Lynda Horn
Arkansas (Zone 7b)
Eat more tomatoes!
Lover of wildlife (Raccoon badge) Container Gardener Lilies Cat Lover Lover of wildlife (Black bear badge) Zinnias
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gardenfish
Jun 5, 2020 4:26 PM CST
You can cut back. It won't take very long for new growth. Now, this is my opinion. I'm far from being a rose expert! Hilarious!
Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.
Mother Teresa
Name: DrAshish
Newtown, PA (Zone 6b)
Don’t worry, be happy 😊
Drashish
Jun 5, 2020 6:35 PM CST
See photo- Should I spare the healthy looking green areas or knock it all off for best result?
Thumb of 2020-06-06/Drashish/13672c
Thumb of 2020-06-06/Drashish/7a5ee5


Thumb of 2020-06-06/Drashish/19bc58
Thumb of 2020-06-06/Drashish/7c1f4e

If you fail, try and try again
Name: Lynda Horn
Arkansas (Zone 7b)
Eat more tomatoes!
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gardenfish
Jun 6, 2020 2:47 AM CST
You know, I think I would start by cutting out the dead stuff. Then see what happens. The shrubs may look a little uneven at first, but they should put new growth out and it will much better with time. Knockouts are nearly indestructible, but then general rule of thumb for severely trimming all shrubs is only 1/3 of the foliage at a time. I have knockouts at a Master Gardener project of mine, and they got severe blackspot last year, something knockouts rarely have an issue with. I cut them back 2/3 with an electric hedge trimmer. This was in July. They survived and recovered nicely.
Not that I'm telling you to cut yours back by that much! Start slow. You can always cut more, but you can't put it back. I do see what looks like some blackspot. You might want to spray sometime down the road. Copper is good.
Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.
Mother Teresa
Name: DrAshish
Newtown, PA (Zone 6b)
Don’t worry, be happy 😊
Drashish
Jun 6, 2020 10:17 AM CST
gardenfish said:You know, I think I would start by cutting out the dead stuff. Then see what happens. The shrubs may look a little uneven at first, but they should put new growth out and it will much better with time. Knockouts are nearly indestructible, but then general rule of thumb for severely trimming all shrubs is only 1/3 of the foliage at a time. I have knockouts at a Master Gardener project of mine, and they got severe blackspot last year, something knockouts rarely have an issue with. I cut them back 2/3 with an electric hedge trimmer. This was in July. They survived and recovered nicely.
Not that I'm telling you to cut yours back by that much! Start slow. You can always cut more, but you can't put it back. I do see what looks like some blackspot. You might want to spray sometime down the road. Copper is good.


Thank you Lynda. I'm so glad for all the advice on this forums can't believe I only found it now.

If you fail, try and try again
Name: Lynda Horn
Arkansas (Zone 7b)
Eat more tomatoes!
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gardenfish
Jun 6, 2020 12:47 PM CST
That's the thing the gardeners do best on this website, help each other! Hurray! Hurray! Hurray!
Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.
Mother Teresa
Name: DrAshish
Newtown, PA (Zone 6b)
Don’t worry, be happy 😊
Drashish
Jun 9, 2020 12:57 PM CST
I decided to heavily prune -sparing a few branches with leaves. Should I fertilize and or water heavily right after pruning?
If you fail, try and try again
Name: Lynda Horn
Arkansas (Zone 7b)
Eat more tomatoes!
Lover of wildlife (Raccoon badge) Container Gardener Lilies Cat Lover Lover of wildlife (Black bear badge) Zinnias
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gardenfish
Jun 9, 2020 1:44 PM CST
Water, but don't fertilize.
Yesterday is gone. Tomorrow has not yet come. We have only today. Let us begin.
Mother Teresa

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