Red bud trees in large pots

I have two American Redbud and 3 Dogwoood trees in containers on my balcony. They were given to me as bare root trees 2 1/5 years ago. They have been here for two years, the first year they were fine with wonderfull foliage (I didn't know they produce flowers). This spring they budded out however I had no leaves from the buds, they appear to be alive but dormant. I need to keep them in containers on the balcony and want to control the size, is this possible? When do I need to prune and repot, perhaps I need to control the tap root?



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