What is the lifespan of our native sword fern?
The native sword fern, Polystichum munitum, is discussed in local author Sue Olsen’s Encyclopedia of Garden Ferns (Timber Press, 2007). She does not mention the plant’s lifespan except to say that it will suffer and decline with excessive summer heat and humidity (more common in eastern and southern U.S.), and sometimes with long periods of freezing temperatures as well.
Sword fern has a reputation as a tough, long-lived perennial (i.e., returning year after year), and it readily self-propagates from spores, but I have not found any resources which mention the average duration of an individual plant. Most will survive in the Pacific Northwest for many years.