Populus tremula

European aspen is in the willow or Salicaceae family and is native to Europe and Asia, from Iceland and the British Isles east to Kamchatka, north to inside the Arctic Circle in Scandinavia and northern Russia, and south to central Spain, Turkey, North Korea, and northern Japan.

• Leaf is simple, alternate, slightly wider than long, 2–8 cm in diameter, with a coarsely toothed margin and a flat stem (petiole) which allows the leaf to tremble in the wind like leaves of trembling aspen (P. tremuloides). Leaves on seedlings and root sprouts are often larger, heart-shaped to nearly triangular.
• Species is dioecious. Flower catkins are produced in early spring before the new leaves appear, male catkins being green and brown, 5–10 cm long when shedding pollen. Female catkins are green, 2–4 cm long at pollination, maturing in early summer to bear 10–20 capsules each containing numerous tiny seeds embedded in downy fluff.
• Bark may have dark grey diamond-shaped pattern of patches similar to white poplar (P. alba).
• P. tremula hybridises readily with P. alba, resulting in the hybrid known as gray poplar (P. x canescens) which is found widely in Europe.