Such a very pretty yard.
Do you have a dog, if so it will be a tinkle station and ruin your sitting area?
Even if no dog I wouldn't in that particular spot because it is just a thing to trip over and you probably can't see it so well when sitting there. I do see why you would like a splash of color with the quiet little tree in the corner. Maybe bright pink or purple Wave petunias in the pot in front of the little tree, the way the petunias drape would be pretty and probably look nice up against the smiliarily shaped tree. Wave Petunia flowers are tough to kill too which is why I love them.