Andrew coaches at Laurelhurst Park sometimes. Recently, he saw asked some folks wandering around in circles with grocery bags who looked to be picking things up off the ground. He asked some nice older ladies what they were doing, and as it turned out, they were harvesting chestnuts!
He brought me back for a date.
Protip 1. Do not shake branches of the trees or otherwise assault them to try to get chestnuts to fall. Wait for them to fall by themselves. For best results, head out on a windy day. The weather was pretty overcast, chilly, and windy when we went. A great combination for chestnut gathering. Fewer people, more chestnuts falling on the ground.
Protip 2. Do not try to pry open the spiky shells with your fingers. This will hurt. Gently press down on the top of the chestnut shell with your shoe and roll back and forth until you feel it split open. Bend down and pick up your booty!
Protip 3. Bring a bag. If you hang around long enough, there will be plenty for you and everyone else there.