ROSEBURG, Ore. — With their peeling bark and upright form, Pacific madrones are easy to spot from British Columbia to Southern California, but in recent years many Oregon landowners have been calling Extension about trees with brown leaves, dead twigs and trunk cankers.
“They are really beautiful, one of the trees that really stand out in the Northwest."
After a wet spring in 2022, Alicia Christiansen, Oregon State University Forestry and Natural Resources Extension agent in Douglas County, began hearing from dozens of people who were seeing damage on madrone.
“It was a wet spring, perfect for foliar diseases to pop up,” Christiansen said. “People saw the damage and got concerned and started asking a lot of questions.”
To answer those questions she organized “All About Arbutus,” a workshop that drew about 70 people. Some, like Seattle resident and madrone advocate Terry Nightingale, traveled a long way because they wanted detailed, research-based information.
“They are really beautiful, one of the trees that really stand out in the Northwest,” said Nightingale, who hopes to plant madrone on a slope behind his home.
Why madrones struggle
Madrone, Arbutus menziesii, is native here but it can be fussy. It prefers sun and well-drained soil. When it is planted or grows where soil holds water, it becomes vulnerable to several diseases.
Much of the damage comes from Phytophthora, a group of plant-pathogenic microorganisms best known for historic potato blight and now recognized as the No. 1 disease problem in nursery crops, said Dave Shaw, OSU Forestry and Natural Resources Extension forest health specialist.
Phytophthora species and other fungi can infect madrone roots and stems. Symptoms can include:
- Leaf spotting
- Twig and tip dieback
- Cankers on trunks and larger branches
“The more we use molecular techniques to identify fungi we realize that field diagnosis is problematic,” Shaw said. “We need to gather the fungi and take it back to the lab. That is a lot of work and takes money. Funding for madrone research is miniscule compared to commercial species like Douglas-fir.”
What the workshop covered
Christiansen and Shaw were joined by Marianne Elliott, plant pathologist at Washington State University, and Michael Yadrick of Seattle Parks and Recreation. Elliott explained that Phytophthora is common in irrigated areas and with infected nursery stock, but it is also now found in wild sites. The panel emphasized that several different pathogens can produce similar symptoms on madrone.
They also stressed that site and climate matter. In shaded, humid forest edges beneath large Douglas-fir, disease pressure can be higher. In open, sunny spots with good drainage, trees tend to look better and tolerate summer drought.
Management steps for landowners
Extension specialists suggested these practices for people trying to keep madrone on their property:
- Plant madrone in full or nearly full sun.
- Choose sites with excellent drainage; avoid chronically wet or irrigated areas.
- Do not irrigate established trees — extra water can favor disease.
- Prune out dead or blackened branches.
- Rake up and dispose of fallen, infected leaves and twigs.
- Clean pruning tools between trees.
Details are available in the OSU Extension publication Forest Health Fact Sheet: Diseases and Insect Pests of Pacific Madrone, and Washington State University maintains an informational madrone website.
Climate and future outlook
Elliott said the pathogens that affect madrone have been present for a long time, but warmer, drier summers followed by wet springs can make problems look worse.
“The diseases have been here,” she said. “The difference is climate change and urbanization. Hot summers — drought — cause root disease and stem cankers to be really aggressive and can cause dieback.”
Some landowners, like Steve Hart near Roseburg, have recently lost trees and wanted to know how to protect the rest. After the workshop, participants said they had clearer guidance on siting, sanitation and pruning so they can keep working with a tree that has deep meaning in the Pacific Northwest landscape.
Previously titled Enthusiastic crowd attends OSU Extension workshop to hear about iconic madrone tree
