Monkey puzzle trees are highly distinctive, with mature trees possessing a tall, straight trunks and an umbrella of branches at the crown (4). Young monkey puzzles have a 'christmas tree' shape, with branches on the lower parts of the trunk which are later shed (5). The smooth bark is greyish-brown in colour (2) and can be up to eight centimetres thick (4). The horizontal branches emerge from the trunk in whorls of three to eight and the tree is covered in scale-like leaves all year round (4). These trees are mainly dioecious; different trees bear flowers of different sexes. The large cones develop in the upper branches (6) and bright orange-brown seeds are released (2).