If you use Blender 2.9x and want to hide the instanced leaf of the tree in the viewport as well as in your rendered image, the leaf must be outside the "Collection" for the tree in the "Tree" file that you link in your "Piero" file:
The rendered view in Cycles:
Unchecking the "Exclude from View Layer" for the "Collection" with the leaf doesn't have any effect on the linked tree.