Western Sword Fern Dieback

Introduction

Within the last decade, observations throughout the Puget Sound Region have indicated a dieback phenomenon affecting western Sword Ferns. These reports were based on observations from both land managers and concerned citizens. The symptoms of this dieback include foliar browning, tissue rot, the presence of fern stumps (remnants of the ferns’ short stalks), and the plant’s eventual death.

The Western Sword Fern (Polystichum munitum) is one of the most vital & recognizable plants in the Pacific Northwest. The Western Sword Fern is a stable to our forests and holds cultural, ecological, and economic value. Its pinnated structure and hardy green leaves stand out in our forests, which make it more recognizable when they are unhealthy.

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The Importance of Swordferns

Vital to the Vibrant Understory

Sword fern (Polytichum munitum) is a major component of the understory of the coastal forests of the Pacific Northwest. It provides many social and ecological services.

Ecologically, sword fern provides nutritional value to mountain beaver, deer and elk. It is also provides critical habitat for many species and serves as important source of cover during breeding ceremonies of Pacific ruffed grouse. Sword fern also has the ability to resprout after disturbance and is important for nutrient cycling, erosion prevention and soil health.

Culturally, sword fern has served many purposes for indigenous communities in the region. It has a rich cultural heritage because it has been used in games, ceremonies, as medicines, as fibers for mats, rugs and beds, and it can provide nutritional value during critical times of need such as during famines or seasons with limited food availability.

Dieback symptoms

Report New Sightings

Share Your Observations on iNaturalist

Join the project on iNaturalist.org to share observations of western sword fern die-off. Observations can be uploaded from a computer or with the iNaturalist smart-phone application.

eight small square pictures in two rows of four, all of western sword fern

map showing observation locations, mostly in the general Seattle area and some also in Mt Rainier National Park.

View more observations from “Western Sword Fern Decline in Washington State” on iNaturalist

Soil Sample Collections

Join the project on iNaturalist.org to share observations of western sword fern die-off. Observations can be uploaded from a computer or with the iNaturalist smart-phone application.

Swordfern Health Watch – iNaturalist

Western Sword Fern Dieback Research – WSU Urban Forest Health Labs

Images of Ferns at a site in June 2011 compared to images of Ferns at same site in May 2017 — Images of healthy sword fern on the left in 2011 and the same site in 2017. Photo collage above by Paul Shannon

The sun shines through a dense mixed broadleaf forest, highlighting three sword fern plants in a row. The one furthest from the camera is just in front of a log that fell long enough ago to be losing its bark with some visible decay to the exposed wood.

More Information and Resources

Strategic Plan

Seward Park Sword Fern Decline Strategic Plan, Sword fern decline working group, Seattle Parks and Recreation, Green Seattle Partnership, December 2018.

Websites

Sword fern decline at Seward Park, Green Seattle Partnership.
Sword Fern Die-off, Pacific Northwest Pest Management Handbook, Oregon State University.
Swordferndieoff.org, Irene Natalie.
Seward Park Sword Fern Dieoff Blog, Paul Shannon and Catherine Alexander.

News Articles

Nelson Paul, Good news about Seward Park’s Mysterious fern die-off, South Seattle Emerald, December 4, 2019.
Doughton Sandi, The case of the vanishing ferns: citizen sleuths can’t figure out what’s killing Seattle’s sword ferns, The Seattle Times, March 28, 2019.
Morrison Kyle, Sword ferns in Seward Park, Parkways, Seattle Parks and Recreation, December 21, 2018.
Sooter Tad, Ferns are dying in Kitsap forests, and nobody knows why, Kitsap Sun, September 15, 2018.
Deweerdt Sarah, The mystery of the missing ferns, Sierra Club, August 17, 2017.
Nelson Paul E., Seward Park fern die-off (an interview with Paul Shannon), South Seattle Emerald, August 15, 2017.
King 5 Staff, Massive mystery fern die-off at Seattle park, King 5 News, June 16, 2017.
O’Neill Eilis, Sword fern mystery: acres of dead forest plants puzzle scientists. Oregon Public Broadcasting, KUOW/EarthFix, July 27, 2017.

Blog Posts

Are extreme temperatures contributing to the Seward Park sword fern die-off? Joe Zagrodnik, January 30, 2019.
Mysterious die-off threatens Seward Park, Denise Dahn, Seattle Nature Alliance, May 16, 2017.

Presentations

Emerging forest health issues: sword fern die-off and Pacific madrone decline (PDF 35MB), Marianne Elliot, Washington State University, Northwest Washington Forest Owners Winter School, February 29th, 2020.
Seward Park sword fern die-off (Link), Tim Billo, University of Washington, Washington State Native Plant Society Lecture, January 3, 2019.

YouTube

Sword fern die-off, Kitsap Peninsula, Paul Shannon.

Focus on four sword fern fronds pointing directly upward. The two on the left still have their upper leaves curling and the ends of the fronds are just exiting the spiral stage.

a new sword fern frond with its leaves still all curled in, curling more tightly towards the lower part of the frame where the end of the curling fiddlehead shows still nearly in a spiral