[ Don't worry, Red will be here to ramble away the details for him! ]

Evolution is instantaneous! But she trained hard to do it. They say there's signs when an ivysaur is getting close to evolving, like a sweet smelling coming from her flower. She still has that now; it's really nice.

But the thing about evolution is that one moment they're standing there, then they're covered in a white light and the whole of their body changes shape! Not all pokémon become really big, but venusaurs do.