I’m having a really hard time remembering the name of a book series… It was about two children who find trees that when climbed take them to other worlds. There were many different trees and each one went to a different world/place, I’m pretty sure the trees talked or something like to. It was an adventurous fantasy, not scientific.
Might this be The Faraway Tree series by Enid Blyton...?
Book 1: The Enchanted Wood (1939)
Book 2: The Magic Faraway Tree (1943)
Book 3: The Folk of the Faraway Tree (1946)
Book 4: Up the Faraway Tree (1985)
The Wikipedia page provides an overview of the plot:
The stories take place in an enchanted wood in which a gigantic magical tree grows – the eponymous 'Faraway Tree'. The tree is so tall that its topmost branches reach into the clouds and it is wide enough to contain small houses carved into its trunk. The wood and the tree are discovered by three children named Jo, Bessie and Fanny (later updated to Joe, Beth and Frannie), who move into a house nearby. They then go on adventures to the top of the tree.