In the South East USA we have a wide variety of Blue Berries. Some grow on short ground cover type bushes and others grow on bushes that can be 12 feet tall and big and round.
The State Agriculture departments have encouraged the development of cultivars that have profuse and tasty output. The cultivars are based on endemic stock so they not only thrive but they also volunteer pretty well.
They are all capable of making your teeth turn blue. :-)
We also have "Sparkleberries" which look very similar but taste more mealy and tart. They aren't just tart blueberries but they look real similar to a lay person.
We also have wild plums, but only one out of many trees has tasty fruit so if you know of a good tree out in the forest you are probably not telling anyone ;-).