European White Birch

Dominant ornamental birch in Puget Sound lowland installed base, planted extensively 1960s-1990s. Highly susceptible to bronze birch borer (Agrilus anxius); contains 0.6% rhododendrin in bark (Santamour 1999). Summer drought in July-September triggers BBB colonization. Most B. pendula in regional landscapes will eventually require either proactive BBB management or replacement with resistant species. European white birch is popular for its bark but problematic in the Puget Sound lowlands. Bronze birch borer is the existential threat: stressed trees attract the beetle, larvae girdle branches, and the tree dies from the top down. Our summer drought stresses birch, which brings the borer. The formula for keeping birch alive here is simple: water deeply through every dry summer, mulch the root zone to keep soil cool and moist, and plant in a spot with afternoon shade if possible. Birch leafminer is cosmetic but makes the tree look terrible by midsummer. If you want white bark without the borer risk, Betula jacquemontii (Himalayan birch) is significantly more resistant. European birch is fast-growing but short-lived even under ideal conditions; expect 30-40 years, less with borer pressure.

— Chris Welch, ISA Certified Arborist