CLEAR YOUR KINGDOM OF MONSTERS BEFORE YOU START. The bush will spawn a sludge monster.
It took me just over 300 energy to get 34 maps. Three run through of 56 bushes. The first two run through I always got 2 (sometimes 3) maps. The third run through the monster mostly dropped 1 map.
I am waiting to visit Ivy until asked. You need to visit her for an expansion item (5 Ivy items needed for the first expansion).