Excessive summer irrigation of oak and madrone trees may promote fungal diseases such as the oak root fungus (aka armillaria root disease) and crown rot.
Christmas trees planted in unirrigated sites depend on the weather for survival. A research trial set out to find factors that would help seedlings survive during drought years. Results were mixed.
This article briefly discusses the most prevalent madrone disease problems, then offers a broader perspective on the health of this southern Oregon native.