In the previous games of Animal Crossing, players were able to plant money trees. Is it possible to plant money trees in New Leaf? If so, how?
Money trees are still possible to plant. According to the Animal Crossing wikia, they do appear in New Leaf. You need to bury a bag of money with a Golden Shovel in order to plant a money tree, and you then get a chance that the Money Tree will grow based on how much money you planted in the ground.
As the wiki states,
This chart from the same wiki shows you the probability of the Money Tree growing, along with the expected reward from the tree.
Note that it is on average never profitable to plant money trees.