Betula occidentalis odorless when scraped. The leaves are alternate, ovate to rhombic, long and broad, with a serrated margin and two to six pairs of veins, and a short petiole up to long. The flowers are wind-pollinated catkins long, the male catkins pendulous, the female catkins erect. The fruit is long and broad, composed of numerous tiny winged seeds packed between the catkin bracts. The identity of similar birches in Alaska is disputed; some include them in "B. occidentalis", while others regard them as hybrids between "Betula neoalaskana" and "Betula glandulosa". Some Plateau Indian tribes used water birch to treat pimples and
Pterocarya fraxinifolia appear in April, the male catkins thick and green, 7.5 – 12.5 cm long, the females longer with less dense flowers, bearing red styles forming fruiting catkins 30 – 50 cm long, the green, winged, nuts approximately 1.8 cm wide. The species is fast growing and grows best on flat ground or shallow slopes near river banks and in deep moist soils. The climate associated with the distribution of this tree includes mild winters and mild humid summers. It generally grows in mixed stands with other species and rarely grows in pure stands. Fossils of "Pterocarya fraxinifolia" have been described