The pilot was taxiing to the north, on the west side of the runway outside of the runway markers in preparation for takeoff. While maneuvering the airplane around a pothole, he lost sight of the windsock pole in the clutter of trees lining the airport boundary. Subsequently, the left wing struck the windsock pole, resulting in substantial damage to the wing spar. The pilot reported no preimpact mechanical malfunctions or failures with the airplane that would have precluded normal operation.