Here's my take of a realistic Ivysaur, I'm basing my design largely off of a Bearded Dragon, and I am also taking some inspiration from RJ Palmer's design, but also trying to add in some of my own design elements as to how I would think a realistic Ivysaur might look like.
And here is the Pokedex entry for Ivysyaur:
The Seed Pokémon, Ivysaur, Bulbasaur's evolved form. The bulb on its back absorbs nourishment and blooms into a large flower.