Found by Valhalla of Morningthaw: I found a "Tree" in the desert, it looked like a pile of rocks, and its description read "A rock". below is the message I received when handing the "Tree" to the Stone Craftsman.
You allow Stone Craftsman to examine your Tree.
You hand over 1 of your Trees.
Stone Craftsman tells you, "Thank you human, this will do nicely. Before long we'll have this place filled with little benches to sit on."
Stone Craftsman tells you, "I have come here to show my support of the upcoming marriage, lending a hand with what I know best. I need rocks so that I may form them into benches fit for tiny human forms."