Can be used to trade.
+3 for retrieval, +3 for opening, -3 for giving away.
Just pick a walnut off the ground (circled in image to left).
You will loss points if you give the walnut away.
The walnut tree seems to have dropped a special walnut on the ground, and it just so happens you pick it up. After you pick up the walnut, use it on yourself. This will cause Graham to open it and discover that it is made out of gold.