Trees are organized alphabetically by genus and species. Hover over a photo series to control the images.
Cottonwood (Populus deltoides)
There seem to be many opinions as to how to classify Albuquerque's cottonwoods. One popular option is Populus deltoides wislizeni.
In the spring, catkins with any amount of red indicate a male tree, while all-green catkins indicate a female tree. The females then produce thousands upon thousands of tiny seeds, each with "cotton" to help them spread in the wind. This cotton accumulates where it's not wanted, but cottonwoods are not entirely to blame—the local willows produce "cotton" as well.
Young cottonwood leaves are a beautiful emerald green but become duller 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 slow, 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.
The New Mexico Wildflowers app shows 31 species of Salix, and the SEINET checklist for Bernalillo County lists seven species. Many species look similar and some species hybridize. Detailed information sources are not always helpful to duffers like me. Take, for example, the SEINET web page for one of the local species, peach-leaf willows (Salix amygdaloides). The web page explains that for this species, “the leaf blades are usually dull on the upper surface, bearing rudimentary stipules” and that I should look for “glabrous branchlets.” Stipules? Glabrous? The page also mentions that this species of willow is also known as Salix amygdaloides var. wrightii, Salix nigra var. amygdaloides, Salix nigra var. wrightii, and Salix wrightii.
Not being a botanist, I have a mental checklist that begins by dividing local willows into narrower-leaved and broader-leaved. The following applies to the seven species on the Bernalillo County checklist.
The narrower-leaved willows include the aptly named narrow-leaf willow (S. exigua) and Goodding’s black willow (S. gooddingii). The SEINET web page for narrow-leaf willows now comes to the rescue: S. exigua “is one of two willows that can be found along low-elevation rivers in the Southwest. The other, S. gooddingii, grows into a well-developed tree with lanceolate leaves 9–16 mm wide, with toothed edges. S. exigua, in contrast, is clonal and tends to grow in dense thickets; it never grows into a well developed tree, but instead has many woody stems only a few centimeters in diameter; and the leaves are much narrower, only 2–9 mm wide. Look also for the young branches which are often distinctly red-brown.”
Thus, my mental checklist for narrower-leaved willows along the local Rio Grande turns actual trees into Goodding’s black willow, while dense thickets of “baby” willows (often with reddish branches) become narrow-leaf willows.
The broader-leaved wild willow species in my home county include the aforementioned peach-leaf willows, Bebb willows (S. bebbiana), dewy-stem willows (S. irrorata), and shining willows (S. lucida). While I don’t feel the need to break them down further, it seems that people tend to refer to broader-leaf willows in the Albuquerque and Corrales Bosques as peach-leaf willows.
Finally, the leaves on arroyo willows (S. lasiolepsis) fall somewhere between narrow and broad. I'll cross that bridge when I come to it.
Anyway, that (plus taking photos to check later) is what works for me. Maybe it’ll work for you as well.