How about a pair of apple trees? Persimmons?

1. a 4 x 4 planter isn't large.
2. a permanent planting will need to be very hardy to survive outside.
3. because of 1. and 2. most people around me don't plant for the winter, but decorate. Annuals are planted for summer, and things like painted branches, evergreens, bows, ribbons, sparkles are used for the winter.

A picture would help. 4 x 4 sounds quite big to me. Are they on top of the deck with bottoms. Or let into it and built on the ground? What are the sides made out of?