Bloom all flowers before going through the stone wall, and a green flower will 
  appear.
  After the rock wall opens, bloom all the red flowers in that area, then all 
  the yellow flowers. A green flower will appear on a sort of rocky outcropping.
  Enter the last area with the three formations surrounding the larger center 
  one. Do not follow the blue flowers. Instead, go left around the edge of the 
  canyon. Go past the blue flowers, look towards the mountain, and follow the 
  path going up the mountain to find a green flower.