It's hoped you began your winterizing when you planted your Don Juans by burying the bud union 4-6 inches below the soil surface. Don Juan is not especially hardy. Nothing you can do to the canes will keep them viable until next spring. If you didn't bury the bud union your Don Juan will most likely not survive the winter, no matter what you do. Burying the bud union and covering them with leaves or digging a trench next to the bush and burying it by tipping it over in the trench and covering it with soil are probably the only recourse you have in your zone 4 to hope for any type of survival.
I've stopped trying to grow Don Juan after many tries over many years. First year was good but they always died after a year or two, no matter what I tried to do for winter.
Too bad as it has a nice fragrant bloom. I planted one for my son in Florida and it grew 20 feet canes covered with blooms most all year. If mine survived a winter it would only get about 6 feet tall at most.

To winterize Don Juan here in MN, the best approach is to dig him up and ship him to Florida for the Winter and have him sent back next spring.

I have given up. Even when I buried the whole plant over winter he died. Too bad, it is a nice rose - just not one for MN and similar climes.

When I asked at the garden center why they sold such a tender rose they said "Well, some folks like to grow them as annuals".

Good luck.

Charles

That does not sound very promising. I have the plants between my 6 x 6 deck posts. I think I will wrap aroun the posts and fill with leaves and mulch. I will do what I can to keep them.

If they do not make it, what is a good climbing rose for my zone?

I have grown three climbing roses from the Canada rose breeding program that are cane hardy here in MN zone 4a. They are William Baffin, John Cabot, and John Davis. They are really large shrubs that can be trained as climbers, but completely winter hardy except for tips and late season new growth.

WB is the most hardy and disease resistant, however I have never seen any repeat flowering despite claims to the contrary. WB is also very vigorous to the point of being difficult to control. He will turn into a small tree or a thicket if left alone.

John Cabot is relatively easy to train on an arbor or trellis, but also has a tendency to spread out. Moderate to light repeat that varies from year to year for no apparent reason. To my eye, the flowers are more appealing than WB's. Blooms are semi to lightly double in a fuschia tinged pink. Can get minor fall spots if not sprayed.

John Davis is, I think, the most civilized of the three. The four inch flowers are clear pink and fully double. JD is the least vigorous, but still a good grower after the first two years. JD has a reliable repeat. JD can get a touch of Powderey Mildew in years when PM is around.

Quadra and Rambling Red are two red climbers that grow OK here, but both have moderate to severe die back in the winter. They do not have the spectacular spring flush of bloom that the first three do, but are consistent bloomers over the season. Because of the winter kill, they do not get over six to seven feet for me and show no sign of getting out of hand.

Three climbers that I grow as pillars or tall bushes because they die to the ground or mulch line every winter might be worth trying if you are willing to do extensive winter protection are:
Climbing America, Golden Arctic, and Roberta Bondar.

Good luck.

Charles

Very few climbers will survive cold winters unscathed.
That said, I grow a few that give me very nice late spring flushes after having died back each winter, some more than others.
Those in my zone 5 a that are relatively hardy are Fourth of July and Autumn sunset, both had to be trimmed back to 2-3 feet this spring but are blooming nicely now and usually always have blooms on them. New Dawn only requires a light pruning. Dublin Bay is a nice hardy red. Others are Viking Queen, City of York, Compassion, Berlin, Leverkausen, Morgengrub, Dortman, Coral Dawn, and Berries and Cream. All mine are own root and have been in the ground a minimum of 3 years. Any grafted climbers had the grafts buried 6 inches deep and are now on their own roots. My Fourth of July, Berries and Cream, and Autumn Sunset were originally grafted. This year I've planted Pele' and Aloha bare roots and will see how they do.
I don't winter protect but it's been a few years since we've had winter temps colder than minus 10.
Although not a climber, my Jens Monk is a tall hardy Explorer hybrid rugosa that repeats well.
I've had similar experience with the Explorers mentioned in the post above although my Quadra did have a nice spring flush and is reblooming well this year. This is it's first good year after 3 dud years,