A picture with oak tree bark covered with green moss. These trees have the strongest, broadest, and deepest root system. Oak grows into a large tree with valuable wood. There are a total of 450 species of oaks in the world. The durability of oaks is amazing. Oak tree bark jigsaw puzzle shows one of the most durable trees. Play and solve Oak tree bark puzzle with 12, 24, 35, 40, 54, 60, 70, 96, 104 or 260 pieces. This online jigsaw puzzle, is the perfect way to relax. Or create your own custom puzzles from photos.