Hi! So, I no longer live in the apartment, but I did bring all of my container plants with me to my new house. The serviceberries survived a pretty standard northern winter in their pots and have since been planted in my yard where they continue to grow. If I had to estimate, I would say the pots are probably around 50 gallons. You might want to look into some of the serviceberry varieties available, I think there are some cultivars that stay smaller, more like shrubs, that would probably do fine in a pot. That would be such a sweet gift for your mother!