The Aspen (Populus tremula) is a medium-sized deciduous hedge growing to 10–25 m tall, with a trunk up to 1 m diameter. The bark is pale greenish-grey and smooth on young trees with dark grey diamond-shaped lenticels, becoming dark grey and fissured on older trees. The leaves on seedlings and fast-growing stems of root sprouts are very different, heart-shaped to nearly triangular, and often much larger, up to 20 cm long. Adult leaves, produced on branches of mature trees, are nearly round, slightly wider than long, 2–8 cm diameter, with a coarsely toothed margin and a laterally flattened petiole 4–8 cm long.