Question
QUESTION: I have had two unsuccessful attempts in keeping my knockout rose trees viable over the winter in Cincinnati, Ohio. The first year, I has them potted in large pots, the second planted in the ground. Both of these times they remained outside for the winter.
They were all growing luxuriantly as winter hit, but perished and did not return in the spring. I have 16 knockout rose bushes surrounding them in my landscape that always return healthy and vibrant. As winter approaches again, I am searching for some expert advice to keep my new knockout rose TREES alive.  They are currently in very large urns that I intended to move in to the garage for the winter. Can you please offer your insight and knowledge as to the best way to keep these trees alive in my climate?  They look beautiful adorning the front entry of my home, but the trees are a little bit pricey to be annuals so this may be their last chance with me!  Thanks a lot!

ANSWER: In your climate you should have no problem keeping Knock Out roses alive over the winter. However even though your climate is considered having a mild winter, many times roses are killed by the temperatures fluctuating. Rose trees are not really hardy as the rose sits up in the air and this means you can't protect the bud union at the base of the long stalk. Many gardeners do well with wrapping their tree roses with bubble wrap and then tying it snugly at the base of the tree and again just under the base of the rose on the top. The garage is anther good place providing it doesn't get heated. Also if you are going to bring the trees in for the winter, don't do it until the rose is completely dormant, as then there will be no chance of heat activating it into growth again. If you bring the rose in before it has drawn down all the sap, any small amount of warmth starts the sap rising , then it gets cold and this kills or damages the frail growth. It makes for a poor rose bush in the spring. It isn't the Knock Out rose that died but the bud union that joined it to the long stalk that died. Give the rose about 1 cup of water each month just to keep the soil on the damp side but never wet or you will encourage molds. In the spring do your usual pruning on the tree, sprinkle some slow release Osmocote 14-14-14 all around the base and that should be all that you need in regards to fertilizing for the season.

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QUESTION: Thank you, your information should save my knockout trees this year. The winter temperatures here do routinely fluctuate on a wide scale. I am
just wondering several things related to your answer.  First, will it help even more if I wrap them in bubble wrap and bring them in to the garage? Second, I am not certain when the rose is completely dormant.  Must it drop all leaves, or just have no evidence of continued growth? Lastly, when should I return it to the outside landscape?

Answer
When the rose draws down the sap from it's canes, this makes the leaves fall off because they are now dead. So when all the leaves have fallen off you then know that the sap is in the roots. Of course there are other things taking place in the rose's chemicals but all one really needs to know is that when the leaves have gone the rose is dormant. So let the rose sit outside until the cold has made it go dormant.In regards to the bubble wrap. Roses will start to activate into growth even when the temperature is around 40'. You want to keep your roses below that. If you make a blanket around the rose it could act like a greenhouse. However if the garage is not insulated and the temperature gets below freezing a lot in there, then use bubble wrap. But your area isn't one that gets a really nasty winter and because the temperatures do fluctuate, if you feel safer using bubble wrap, then only wrap the container not the whole bush and that should not encourage the plant into growth.
When spring starts and the weather gets warmer, you will see the rose start to make new leaves. Then take the wrap off and place it where there is some sunlight such as a by a window.  In the spring when there is no chance of frost for three consecutive days, you can then place the rose outside. Frost won't damage a rose it is when the cold carries on for three days that the damage is done to new growth.