Western Sword Fern Decline in the Pacific Northwest

What could be more iconic of the PNW than a lush fern understory? Unfortunately, previously healthy stands of western sword fern (Polystichum munitum) have been declining throughout the Puget Sound Region (western U.S.) in the course of the past decade. The cause of the decline is not yet known and we need your help to identify potential sites where sword ferns may be affected.

This effort began after acres of sword fern were impacted at Seward Park in Seattle, WA. Large stands of sword fern within the park have been lost, with no subsequent regeneration. Symptoms began with foliar browning, rotting, and discoloration, eventually leading to plant mortality (die-off), leaving fern stumps that do not regenerate. This should not be confused with fern fronds that are browning after drought, or appear flattened after snow melt. The extent of the decline is typically severe.

Additional Resources:

Green Seattle Partnership Seward Park website:
https://www.greenseattle.org/information-for/forest-steward-resources/restoration-resources/gsp-research/sword-fern-decline-at-seward-park/

https://www.sierraclub.org/sierra/mystery-missing-ferns

http://archive.kuow.org/post/sword-fern-mystery-acres-dead-forest-plants-puzzle-scientists

https://www.king5.com/article/tech/science/environment/massive-mystery-fern-die-off-at-seattle-park/449774277

A personal blog by a Seward Park forest Steward (Paul Shannon): http://sewardparkswordferndieoff.blogspot.com/

*The views and opinions expressed in the blogs and news articles are those of the authors and do not necessarily reflect the official position of Green Seattle Partnership or Seattle Parks and Recreations. less ↑