U.S. Episode # 48:

Bulbasaur's Mysterious Garden 

This story starts with Ash battling with a man, the man chooses Rhyhorn so Ash chooses Bulbasaur.Rhyhorn hits Bulbasaur in the head so Ash calls him back; but, Bulbasaur refuses and the battle continues.When Rhyhorn is attacking Bulbasaur, Bulbasaur uses Razor Leaf, then he finishes Rhyhorn with Vine Whip. Then Bulbasaur´s bulb starts brighting.

Now is a special time where all the Bulbasaurs gather in the Mysterious Garden that very few humans have seen. The Bulbasaurs use special pollen from a Venusaur that evolves them into Ivysaurs, but Ash’s Bulbasaur doesn’t want to evolve. As the group of pokémon tries to force Bulbasaur’s evolution, Team Rocket drops in to steal them all. However, Ash’s Bulbasaur blasts of Team Rocket by using.So, Bulbasaur is left in peace to decide for itself when it wants to evolve.

I hope this will help you