Trees are organized alphabetically by genus and species. Hover over a photo series to control the images.
Cottonwood (Populus deltoides)
Populus deltoides and P. fremontii form a genetic continuum, in addition to being similar. Like most people, I'm happy to call all trees of this type "cottonwoods" and leave the finer divisions to the botanists.
Cottonwood leaves are emerald green in the spring, but are increasingly dull as the summer wears on. If the fall begins with a sharp frost, the leaves turn to gold all at once and the effect is spectacular. If the fall cool-down is less abrupt, leaves turn yellow and then brown separately and the fall color effect is more muted. Leaves often stay attached long after they've died.
Quaking Aspen (Populus tremuloides)
Usually just referred to as aspens, these trees have leaves that resemble those of their cousins, the cottonwoods. But aspen petioles (leaf stems) are flattened rather than round in cross-section, so the leaves twist around in the slightest breeze. Hence the "quaking" part of the full common name. They come into their glory in the fall, when the golden leaves contrast with the white-barked trunks. Very rarely, aspen leaves turns red instead.