I am basing my question on what I infer from this answer. Excerpt:
Tosefos there (Brachot 40a) actually suggests that all berries should be borei pri ha'etz based on that standard, however he brings from the Yerushalmi that fruit of brambles/thorn bushes are pri ha'adama.
Another par. in that answer states:
The basic requirement of borei pri ha'etz is being perennial, as you mentioned, based on Berachos 40a
In describing blueberries, this Wikipedia article states that they are perennials, so that would qualify them as Ha'etz. However, it also describes various blueberry species, many of which grow on bushes. AFAIK, none have thorns (if that is an absolute requirement based on Yerushalmi definition.)
So, practically speaking in terms of ruling, now, is there a definitive bracha or is it based on which species you are eating?