Bulbasaur's Mysterious Garden is the 51st episode of the Indigo League season.
Ash and his crew are still on a tough path to Cinnabar Island. After battling his way through many trainers, he comes across a Hiker. This dangerous trainer desides to battle Ash and sends out his Rhyhorn. Ash, accepting his challenge, sends out Bulbasaur. Bulbasaur, unwilling to give up endures Rhyhorn's strength and defeats it. After the two trainers chat, Ash finds out that Bulbasaur isn't feeling so well and the bulb on his back starts glowing. The worried Ash brings Bulbasaur to the Pokemon Center to have Nurse Joy examine him. After examining him, Nurse Joy tell Ash that it is preparing to evolve, this making Ash very exited. After showing them a garden of blooming flowers, Joy than informs the friends that Bulbasaur gather from all over the world to attend a festival where they evolve. The festival takes place in the "Mysterious Garden". Bulbasaur overhears all of this.
That night, Pikachu wakes up to Bulbasaur walking out of the Pokemon Center. Pikachu follows Bulbasaur all the way to a garden where some other Bulbasaur pick him up with their vines. Pikachu trys to help Bulbasaur, but he makes Pikachu stop. Pikachu than races back to the Pokemon Center to get Ash. He wakes Ash up and leds him to where Bulbasaur was. Meanwhile, Team Rocket finds the group of Bulbasaur and trys to capture them. This ended in no positive results. Back near the Pokemon Center, Ash, Misty, and Brock follow the pollen to try and find Bulbasaur. However, vines try and block their path. Eventually, they find a garden filled with Bulbasaur. These Bulbasaur than start chanting and all of the pollen goes directly to a tree, making it grow very high. A Venusaur than emerges from inside the newly-grown tree. After chanting some more, this time with Venusaur, the Bulbasaurs all start to evolve. Ash's Bulbasaur wasn't chanting, so he did not evolve yet. Ash, starstruck by the sight of evolution, wonders if his Bulbasaur is going to evolve. His Bulbasaur is trying not to evolve, much to Ash's surprise. The newly evolved Ivysaurs and Venusaur than get angry at Ash's Bulbasaur and Venusaur trys to hit Bulbasaur with it's Vine Whip attack, but Ash interupts and takes the hit for Bulbasaur. Ash apologizes for showing up, as humans are not allowed, but he know that he has to protect his friend. Venusaur trys to convince Bulbasaur to evolve by manipulating nature, but Team Rocket enters the forest via balloon. Team Rocket starts sucking up all of the Ivysaur and the Venusaur. Ash commands Bulbasaur to "blow them out of the sky", but he fails. The sun's rays start to shine on Bulbasaur's bulb and Dexter the PokeDex informs Ash that it is preparing to use Solarbeam. Bulbasaur blasts the balloon with his new attack and free all of the Ivysaur. Team Rocket falls out of their balloon and all of the other Pokemon want revenge on Team Rocket. They all smack Team Rocket with their vines and make them "blast off again". Venusaur than lets Bulbasaur leave and is now okay with him not evolving. Ash and his crew continue their quest to reach Cinnabar Island.