Answer: Have you considered Crape Myrtle, Albizia, Golden Chain or Hawthorn? They'll stay small for a long time, each produces seasonal bloom, and all are deciduous. Roots will not be a problem for 10 or more years, but tree roots traditionally explore as far out as the tree's height. So, a 20' tree will have roots travelling out 20' in all directions. If there's not enough room for that kind of root spread in your patio planter, you might want to consider a large shrub instead of a small tree. Shrubs can be trained to look like trees. I've seen some spectacular Wisteria's trained into a umbrella-shaped trees. You can do the same with Camellia and Holly (although they're evergreen), and with Lilac, Russian Olive.
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