>There are two types of honey trees, normal trees and Munchlax trees. Munchlax trees produce rarer Pokémon more often than normal trees as well as having a chance to produce Munchlax, which normal trees do not have. Only four of the 21 honey trees in the game are Munchlax trees; unfortunately, however, nobody can tell you which ones they are or calculate it for you, because they are determined at the start of your game from your "secret ID", a random number there is no way to access during normal gameplay. Barring the normal/Munchlax tree distinction, the trees are functionally completely interchangeable; SOURCE.
The SID determines your "munchlax trees."