I'm a newbie (to gardening in general and especially trees), so please take what I say with a grain of salt! I'm also in Chicago with a garage rooftop deck and called around to the different nurseries for advise (Jayson, Fertile, Gesthemane). There was some conflicting advice, but I at least two of the three mentioned Crab Apple and Weeping Cherry. I've heard that for a container tree, you should choose something that is hardy enough for two zones below yours (so Crab Apple would fit the bill but Weeping Cherry would not). The other tip that I heard was to buy a sheet of the rigid pink foam insulation and line the sides and the bottom of your container (making sure to cut out the draining hole) to improve the odds of survival. Home Depot sells 24" panels, as well as big sheets that they will cut to size for you. I'm giving that a try in a 24" square container with a Weeping Cherry (and keeping my fingers crossed that the winter is mild).

I am on a 5th floor rooftop and last year I got a shirofugen cherry tree and a paperbark maple and put them in 36 inch wide, double walled plastic containers. I was told those insulate the best over winter. The cherry tree came back with tons of blooms but has since leafed out only on the end of every branch. All of the intermediary leaves died and dropped. The result is a fairly thin canopy.

I am wondering if its the soil or something as its healthy otherwise. I wish i knew what the cause was as i dont want to replace it. The paperbark maple looks sad. Extremely sparse and probably will need to just replace it. I might replace it with a crab apple as well as I have heard they are tough.

I'm too much of a newbie to help. But, the nurseries have told me that it's 50-50 on whether a container tree will survive the Chicago winter (you up your odds by insulating the container). So perhaps it's the effects of winter or the soil or something else entirely. Good luck with the crab apple!

I always suspect a poor soil and too much water when trees don't prosper in pots, so maybe you could use a 5/16" wooden dowel rod, sharpened in a pencil sharpener and stuck deep in the pot as a 'tell' to let you know when it's appropriate to water. I suggest Acer ginnala (amur maple) as a tree that is both vigorous and hardy. It can be grown in tree or bush (multi-trunked) form. As trees go, maples are a little more tolerant of wet feet than the average tree, too. Another good choice would be one of the hornbeams. Korean hornbeam has pretty small leaves and makes a nice tree for container growing.

Al

Just came across this thread 😂 - i am on the northern suburbs of Chicago and I have seven 24“ x 24“ pots that I have never insulated and keep them out year-round for the past 4+ years with emerald green arborvitae and I just this year transplanted them to the side of our house, hoping that they will do well They had gotten too big for the pots and I would just plant some annuals around them in the summer and then in the winter I would decorate with some winter interest.