... Please tell me how to get my Ape to plant trees.

here is the story:
I put the ape on the leash of learning ...
I pick up a tree, and then plant it on fertile ground
I then cast the water-spell on it.
It grows, as do any saplings around it
My ape then picks up a tree (after pointing, scratching his head, and then going "a-ha!" with his hand)
He then promptly picks up a tree, and plants it RIGHT where I planted the last tree.
He then waters it.

He only does this directly after I have shown him. Any ideas?