Venusaur was caught by Nelson during his Pokémon journey through Kanto as a beginning trainer. It is unknown exactly when Venusaur evolved, but Nelson values it as one of his most valuable Pokémon, being used often.
Venusaur is considerably larger and heavier than both of its pre-evolutions, and as such it moves slower than the two when it is not in battle. The bud on its back has since bloomed into a large red flower with six expansive, white-spotted petals, supported on a brown trunk somewhat like that of a palm tree. Instead of patches on its skin, Venusaur appears to have frog-like warts. Additionally, the insides of Venusaur's ears now appear to be red in coloration. Like both his former Charizard and his Blastoise, Venusaur has strange markings on it's body, possibly due to age.
Venusaur are able to manipulate nature, as seen in Bulbasaur's Mysterious Garden by making the flowers on a tree bloom, controling roots and branches to attack Team Rocket or form a defensive wall around the garden. Also, they are able to make Bulbasaur evolve by making their bulbs grow.
As with its pre-evolutions, most of Venusaur's attacks involve the plant on its back; but the attacks are clearly stronger than those from Bulbasaur and Ivysaur. The flower on its back has a pleasant aroma that may attract other Pokémon. The aroma can also sooth people's emotions and calm Pokémon engaged in battle. The fragrance is stronger after a rainy day. The flower also absorbs sunlight to convert it into energy, thus making it far stronger during summertime.
It is also able to charge at its enemies to gain speed, then perform moves such as Skull Bash and Body Slam with a force more powerful than a speeding armored truck. Additionally, it is capable of making incredible leaps for such a heavy Pokémon, and it's able to dodge attacks and jump across close rock formations. Its only downside is that its weight causes a small quake as it lands (of which appears to be the means that Venusaur uses the move Earthquake) which can break the platform it’s trying to land on, or cause it to get buried in mud or sand. Since Venusaur is a fully evolved Pokémon (and the final evolution of a Grass-typed starter Pokémon for that matter), it can use Hyper Beam, Giga Impact, and Frenzy Plant.
It's ability, Overgrow, will increase it's Grass-type moves by 1.5× if the user has less than or equal to ⅓ of its maximum HP remaining