Quaking Aspen
Populus tremuloides · Salicaceae · Deciduous · also called trembling aspen
Quaking aspen is the most widely distributed tree in North America, and it trembles because its leaf stalks are flattened at right angles to the blade so the leaves twist in the lightest breeze. Whole stands are typically one organism connected underground, which is why they turn gold together on the same day.
Quick facts
- Arrangement
- alternate
- Leaf
- Nearly round leaves with small teeth and a short abrupt point, on a stalk that is flattened at right angles to the blade.
- Bark
- Smooth greenish-white to cream with a chalky bloom that rubs off on your hand, darkening and furrowing at the base of old trees.
- Fruit
- Catkins in spring, releasing cottony seed.
- Height
- 30–60 ft
How to confirm it
- Flattened leaf stalk — roll it between your fingers and it is a ribbon, not a rod. This is why the leaves quake.
- Smooth greenish-white bark with a chalky bloom that rubs off.
- Nearly circular leaves with fine teeth.
- Grows in clonal stands that colour in unison.
What it is confused with
One observation settles each of these.
Birch bark peels in papery horizontal sheets; aspen bark is smooth and does not peel.
Bigtooth aspen has large coarse teeth on the leaf edge rather than fine ones.
Where it grows
Across North America, from Alaska to Mexico, and the dominant golden autumn tree of the Rocky Mountains.
Start here: opposite or alternate?
Look at where the leaves join the twig. Are they in matched pairs directly across from each other, or staggered one after another? The vast majority of trees are alternate, so finding an opposite tree removes almost everything else in one step.
In North America, opposite-leaved trees are remembered as MAD Cap Horse: Maple, Ash, Dogwood, Caprifoliaceae (viburnums and elders), and Horse chestnut. That is very nearly the whole list.
Check partway along a healthy twig rather than at the tip, where crowding can make alternate leaves look paired. And check more than one twig.