Sword Fern Die-off
Sword fern is an important species in the forests of the Pacific Northwest. However, many acres of sword fern plants have ‘mysetriously’—as many news articles suggest—died off throughout the Puget Sound.
Researchers and citizen scientists continue to investigate the die-off. See below for updates, more information and resources about the sword fern die-off.
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.
Economically, sword fern is commonly used in floral arrangements and produced for restoration activities.
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.
See the SFDWG Strategic Plan for a summary of insights from research before Dec. 2018.
Observations of the loss of sword ferns from the understory of forests in the Kitsap Peninsula date back to 2010. Additional reports of die-off in sites at Seward Park in 2013 raised substantial alarm. These sites are generally characterized by large circular areas (at least 400sq ft) with uniform patches of die-off and very few surviving ferns.
Sword fern die-off is generally represented by the complete collapse of plants and the absence of regeneration within a close proximity. Symptoms begin with foliar discoloration, browning, wilting and collapse of individual fronds, eventually leading to the death of the entire plant. The absence of the growth of new fronds (no fiddle heads) in a given area in contrast to other parts of the forest may be cause for concern.
No single cause has been discovered and additional research is needed. Many hypotheses have been proposed (see presentations below), but more evidence is needed. Given the die-off is localized and limited to a few areas, researchers suspect the cause is biotic (rather than attributed to drought or other abiotic factors). However, investigations have not revealed an association of the symptoms with suspected soilborne fungi such as Phytophthora or Rhizoctonia.
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More Information and Resources
- Seward Park Sword Fern Decline Strategic Plan, Sword fern decline working group, Seattle Parks and Recreation, Green Seattle Partnership, December 2018.
- 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.
- 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.
- 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.
- 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.
- Sword fern die-off, Kitsap Peninsula, Paul Shannon.
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Many concerned citizens and partners have conducted research to advance knowledge about the cause of the sword fern die-off. Summaries and findings of the research efforts prior to the end of 2018 are available in the Seward Park Sword Fern Decline Strategic Plan produced by Seattle Parks and Recreation and the Green Cities Partnership.
Research projects have included:
- Mapping and monitoring sword fern die-off throughout the region
- Investigating soil and microbial factors
- Confirming that rodent and mammal browse are not primary factors
- Testing for physiological metrics associated with decline
Additional Research is Needed
Research to determine the primary factor driving the die-off of sword ferns is critically needed. Identifying the primary cause will provide vital information for mitigating and restoring the die-off sites and preventing new ecosystems from becoming impacted.