White Alder (Alnus rhombifolia) is a member of the Birch family (Betulaceae) native to western North America, from Washington east to western Montana and south to San Diego County, occurring at altitudes of 300-7900 feet. Though not reported from northern Baja California, it has been predicted to occur there on the basis of its climatic adaptation.

White Alder is a medium-sized deciduous tree. Its pale gray bark is smooth on young trees, becoming scaly on old trees.

The flowers are produced in catkins. The male catkins are pendulous, slender, 1 to 4 inches long, yellowish, and produced in clusters of two to seven. Pollination happens in early spring, before the leaves emerge. The tree produces very large amounts of pollen at this time.

The female catkins are ovoid and mature in autumn, superficially resembling a small conifer cone. The small winged seeds disperse through the winter, leaving the old woody, blackish 'cones' on the tree for up to a year after.

Plant White Alders in moist soils or on the edges of permanently wet areas such as streambanks or edges of regularly irrigated area. These trees grow quickly to 20 feet, and then more slowly. The roots can be invasive, so use caution in deciding where to plant. Due to its ultimate size, White Alder may not be appropriate for small residential gardens.