Alder trees are cone-bearing trees that vary in height depending on the species, and they exist as large trees with single trunks or small trees and shrubs with ample foliage and multiple trunks. Alder trees are native to the Pacific northwest of the United States and produce small woody cones that reach approximately 1 inch in length. Eight species of alder are native to North America, and two of these classify as large trees.
Only two species of alder, the red and white, grow to be large trees. They may reach heights of 40 to 80 feet and resemble oak trees upon reaching adulthood. Unlike oaks and other deciduous trees, however, alders produce cones like evergreens, pines and other conifers. Red and white alders are quite similar in appearance; they have tall, thin single trunks and produce lush canopies of foliage. Their leaf structures vary, however, and are used to distinguish the two species. Leaves of red alders have margins that are tightly rolled under and compact, while white alder leaves are not rolled and appear as broad and flat surfaces. Sitka and thinleaf are two common smaller species of alder: sitka leaves have fine striations and margins that are not rolled. The leaves of thinleaf alders have distinct sets of coarse teeth.