The largest oleander I have ever seen was in my own backyard in Tucson, AZ. I would often cut it back but it would continue to grow, despite the arid conditions.
Oleanders come in several colors and there is even a dwarf variety. The small or dwarf oleanders remind me of my neighbors in Tucson, who had their backyard professionally landscaped. Dwarf oleanders were planted along one side of the house and in a few sporadic plantings. Their flowers were peachy-colored. Very pretty.