Pine resin bleeding from tree bark. Resin extraction consists of incising the outer layers of a pine tree in order to collect the sap or resin. Resin circulates throughout a coniferous tree, and serves to seal damage to the tree. Harvesting pine resin dates back to Gallo-Roman times in Gascony. Tapping pines may either be done so as to sustain the life of the tree, or exhaustively in the years before the tree is cut down.