A slender tree with thin, yellowish-brown or pale bark. Leaves: ovate, short-acuminate at the apex, finely crenulate, rounded or sub-cordate at the base. Flowers: Aments drooping, dense. Fruit: capsule conic, acute, papillose.

The Aspen Poplar is one of the prettiest trees among the mountains, and when the wind blows its tiny heart-shaped leaves, growing on very slender little stalks, tremble with a soft rattling sound. The flowers grow in rather stout catkins.

Populus balsam if era, or Balm of Gilead, has leaves rounded at the base and pointed at the apex, finely toothed, and with slightly revolute margins, that are dark green above and pale green and somewhat rusty below. This tree grows to a hundred feet in height, has stout erect branches, more or less contorted towards the ends, and brown bark tinged with red, which on older trunks becomes greyish and divided into broad ridges covered with closely appressed scales.

Populus trichocarpa, or Western Balsam Poplar, has smooth ashy-grey bark, and stout upright spreading branches. The large buds are very fragrant and resinous, and the leaves, which grow on long stalks, are egg-shaped, finely toothed, dark green on the top and quite pale beneath. The catkins are slender.

Populus acuminata, or Cottonwood, is a much smaller tree than the preceding species. It has stout spreading ascending branches forming a rounded head, very pointed leaves which are toothed except near the apex and base, and pale grey-brown bark divided into broad flat ridges. The bark on the young stems and the branches is smooth and nearly white.