Can you use meganium's pokemon power while meganium is on the bench?

Question

Meganium's power reads " Pokemon Power : Wild Growth - As long as Meganium is in play, each grass Energy card attached to your grass Pokemon instead provides two grass energy. This power stops working while Meganium is Asleep, Confused, or Paralyzed.

Answer 1

You're referring to the Meganium from the NeoGenesis set (#11/111).  Yes, his Pokémon Power is in effect while he is on the bench, as it states "As long as Meganium is in play."  The important part is "in play," as both the Active Pokémon and any Benched Pokémon are "in play."  Interesting side-note, this Pokémon Power would actually be a Poké-Body under modern gameplay!