Water Birch

Water birch (Betula occidentalis, Betulaceae) is a fast-growing shrub or small tree native to western North America, from southern Alaska south to California and New Mexico. It typically reaches 15 to 30 feet tall with a variable, often multi-stemmed form that is upright when young and develops more nodding branches with age. Bark is thin, glossy, black-brown to purplish-brown, non-peeling, with long horizontal lenticels. Small leaves (2 to 5 centimeters) are sharply and doubly serrate, shiny yellow-green above and paler below, turning clear yellow in fall.

Water birch is a riparian species found nearly always along watercourses, growing in sun to part shade on wet to moist soils (pH 5.5 to 7.8), hardy in Zones 2a to 8b. It tolerates clay and wet soils but has low drought tolerance and a minimum root depth of 20 inches. It is a short-lived species that resprouts readily and freely hybridizes with paper birch (B. papyrifera) where their ranges overlap. Documented diseases include rust, canker, and wood decay; pest associations include bronze birch borer, birch leafminer, aphids, and oystershell scale. No named cultivars are in the trade.