From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
New Planet Plant is a planet in the North Galaxy.
Dragon Ball GT
New Planet Plant was the name given to the planet that Baby wished for, an exact replica of the original Planet Plant before the Saiyan-Tsufruian war had begun. Using the power of the Black Star Dragon Balls, Baby resurrected the former Tsufruian homeworld around Earth's orbit. He then began to transport all of his mind-controlled Earthlings to the planet in hopes of creating a new Tsufruian society. It is here that he does battle with Son Goku. During their battle, Goku is easily thrashed around even as a Super Saiyan 3. As Goku lays defeated, he sets his eyes on Earth orbiting high above. This causes him to receive Blutz Waves, sparking his transformation into a Great Ape and then a Golden Great Ape. Goku goes wild and destroys everything in sight. It is not until Pan, his granddaughter, calms him down that Goku remembers who he is, sparking his transformation into Super Saiyan 4. The Super Saiyan 4 form proves to be more than a match for Baby, and the evil Tsufruian resorts to having Bulma Brief (now his slave) create a Blutz Wave-emitting machine that causes the evil Tsufruian to become Great Ape Baby. As the battle between Goku and Baby continues, Old Kaioshin uses the Sacred Water to kill off Baby's mind-controlling infection, releasing all of Earth's people. Son Gohan, Son Goten, and Trunks then arrive on the battlefield in an attempt to offer help. Oob, who had been eaten by Baby after his Chocolate Beam had been redirected, suddenly attacks Baby from the inside. Meanwhile, Gohan, Goten, Trunks, and Pan give their energy to Goku. Once the process is complete, Goku attacks, and in a few short minutes, Baby is severely injured. The parasitic Tsufruian then leaves Vegeta's body and attempts to escape. Goku blasts him into oblivion, however, with a powerful Kamehameha.
Because of the wish made by Baby with the Black Star Dragon Balls, Planet Earth had a mere one year left before its destruction, and that one year had passed. The Z Warriors decided to transport all of Planet Earth's people to New Planet Plant to save them from Planet Earth's destruction. It was unknown what happened to New Planet Plant, but it presumably stayed in Planet Earth's orbit and acted as a replacement for the former Moon.