- With the "Forest of Giant Plants" Stadium in play, could I evolve from Oddish to Gloom to Vileplume all in the same turn?
- Yes. Oddish can evolve into Gloom on the turn it comes into play, and since Gloom has come into play that turn the stadium would allow it evolve into Vileplume right away too.
Source:
Ancient Origins FAQ (2015-08-13), TPCi Rules Team (2015-08-13)