Betula occidentalis aka Water Birch

Betula occidentalis, or water birch, belongs to the birch family. It grows across western and central North America, reaching subarctic areas. Its range runs from Alaska and Canada south to New Mexico. It also grows in California and the Rocky Mountains. This deciduous shrub or small tree grows beside streams and springs. It forms clumps and thickets in damp woodland.

Size varies with the site and growth form. Shrubs may reach 10–15 feet [3–4.6 metres]. Oregon State gives a usual height of 15–30 feet [4.5–9 metres]. Larger trees can reach 40–50 feet [12.2–15.2 metres]. Garden spread may reach 30 feet [9.1 metres]. Plants may have one stem or several trunks. Young plants stand upright, while older branches tend to droop. The crown can be broad, open, and uneven.

Thin bark shines in shades of dark brown, red, or copper. Pale horizontal lenticels mark the surface. Older bark may curl but does not peel in sheets. Young twigs feel sticky and carry small resin glands. The small leaves grow alternately along the stems. They have an oval or diamond shape and toothed edges. Their upper sides are yellow-green, with paler undersides. Fall leaves turn clear yellow. Brown male and green female catkins appear in April and May. Both sexes grow on the same plant. The cone-like fruit breaks apart when ripe, releasing tiny winged nutlets.

Grow water birch in sun or part shade. It prefers fertile, acidic soil that stays moist to wet. It tolerates clay and flooding. Mulch and soaker hoses help keep roots cool and moist. Sources differ on cold hardiness. Missouri Botanical Garden lists USDA zones 4–6; Oregon State reports zones 2–4. Plant groups suit pond edges, stream banks, and wet low spots. It also serves as a hedge. Prune during dormancy, not during spring sap flow.

Leaf miners and aphids can damage foliage. Bronze birch borers may kill weakened trees. Heat and humidity can increase stress. Other problems include cankers, leaf spots, and honey fungus. High-pH soil may cause iron chlorosis. Young leaves, catkins, inner bark, and sap have recorded food uses. Buds and twigs serve as flavourings. Inner bark is a famine food. Bark also supplies dye, containers, and kindling. Birch tar can irritate skin; food uses do not establish general safety.