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Washington State University
WSU Puyallup Ornamental Plant Pathology

Western Redcedar Dieback


Welcome to our webpage about the dieback of western redcedar. The purpose of this page is to provide information about the western redcedar, summarize the dieback, and provide links to other media expressing concern.

Please contact us if you are interested in partnering to advance knowledge or if you have content or information to share.

Forest Health Watch

iNaturalist Link
Forest Health Watch

We’ve launched the Forest Health Watch program to host research projects that anyone can contribute to as community scientists. Check out the webpage or join the Western Redcedar Dieback Map project on to contribute.

Western Redcedar

Icon of the Pacific Northwest

Western redcedar (Thuja plicata) is an iconic species of the Pacific Northwest because of its rich cultural value. Find more information and resources to learn about its incredible cultural heritage below.

The massive size of many trees throughout the region is testament to its capacity for long-term survival. Even after a tree has fallen, its bole can remain largely intact on the ground for centuries.

Western redcedar grows widely throughout our region because of its tolerance to shade, flooding and nutrient poor soils. However, recent observations of dieback and mortality have raised concern about its ability to cope with changes in the climate.

Links to More Information


Biology and Ecology



Relevant Pests and Disease


The western redcedar is critically important to conserve because of its ecological, cultural and economic value.

Ecologically, it provides habitat and nourishment for many mammal and bird species and its tolerance to very wet soils allows it to flourish where other conifer species cannot.

Commercially, it is valued highly because of its durability and resistance to wood rotting fungi. It is also used widely in restoration activities locally and as an ornamental species internationally.

Culturally, western redcedar is considered a Cultural Keystone Species because its multiple uses and value to indigenous North American communities (read more below).

Cultural Heritage

Western redcedar arguably has the richest cultural heritage of any plant species in the Pacific Northwest. Every part, from the roots to the tips of the boughs, can be crafted into useful products that were commonly used by ancient peoples of the Pacific Northwest. For example, foliage and boughs can be used as medicinal products, scented bathing materials, as ceremonial incense, or as rope for binding materials or creating fish traps.

Western redcedar is considered and Cultural Keystone Species because it is a fundamental component of many Northwest Coast cultures (Garibaldi and Turner 2004). These cultures rely on western redcedar for its medicinal properties, nutritional and dietary provisions, role in spiritual practices, and the materials it provides for warmth, shelter, and transportation. Given the clear importance of this is species, it is no wonder why western redcedar is commonly referred to as the ‘tree of life’.

Please contact us if you have any suggestions/corrections for this webpage.

More Cultural Heritage Resources


  • Moerman DE. Native American ethnobotany. Timber press; 1998.
  • Pojar J, MacKinnon A, Alaback PB. Plants of coastal British Columbia. Lone Pine Publishing; 1994.
  • Stewart H, Cedar: Tree of Life to the Northwest Coast Indians, Douglas & McIntyre, University of Washington Press; 1995.

Publications and Reports


Similar Species

Simlar species foliage diversity

Yellow Cedar

Be careful not to confuse yellow cedar with western redcedar. Yellow cedar is best adapted for conditions in Alaska, but the range extends into Washington.

Port Orford Cedar

Port Orford cedar is another cedar that can be confused with western redcedar. This species is most abundant in coastal Oregon and northern California, but is commonly planted as an ornamental species.

Both species are also planted widely throughout the urban areas of cities such as Seattle.

Dead false cedars at Gasworks

Distinguish Western Redcedar

Western redcedars can be distinguished from other cedars by their erect egg shaped cones and the ‘butterfly’ shaped bloom on the underside of leaves.



Unfortunately, many reports of dieback have been noted during the past few years, ranging from Oregon to British Columbia (see below).


These reports generally note trees with thinning crowns, flagging, yellowing or browning of foliage, dying tops and mortality.

The Cause

There is a general consensus among land managers, federal and state natural resource agencies, and WSU Extension Forestry specialists that the driver of the dieback is abiotic. Given its extent throughout the region, it is likely linked with recent drought events, but the relationship has not been empirically tested.

We recommend reading Melissa J. Fischer’s Blog Post (DNR): Western Redcedar East of the Cascades: A Species in Decline? for a thorough discussion of the issue and potential drivers.

dead western redcedar near I90 in Seattle dead western redcedar trees at Gasworks Park, Seattle
Dying redcedar at University of Washington Arboretum

Reports of Dieback Concerns


News Articles

Blog Posts

Did we miss any? Please contact us if you know additional reports or resources to add.


Secondary bark beetle gallary from redcedar bark strip

More research is needed

You can help research go faster by contributing to the Western Redcedar Dieback Map. Learn more about contributing to this project and the Forest Health Watch program at

We are also actively pursuing opportunities to secure more support for research about the dieback of western redcedar. Please contact us if you’re interested in collaborating or supporting research about the dieback of western redcedar.

Observations of bark beetle and fungal associations with dead western redcedar trees have been shared, particularly in trees around Seattle. However, these associations are generally understood to be secondary, infecting the tree after it becomes stressed or dies. More research is needed to confirm or deny this consensus.


How You Can Help

Share Observations

Help accelerate the research by sharing observations of healthy and unhealthy western redcedar trees. Join the Western Redcedar Dieback Map project and share your observations with us on Find more instructions at

Get Involved in the Forest Health Watch
Research Updates

The Forest Health Watch program hosts a visualization of the iNaturalist information here. The visualization updates every day.

The program also hosts monthly Research Update events on MS Teams. Register to attend a Research Update here.

Western redcedar at the University of Washington Arboretum