10 apparently long-dead ferns with miniscule fronds sprouting

Following the suggestion of Betsy Dowling of Zanzibar Landscape Design (Betsy contributed the earthworm hypothesis a few months ago) I today found and photographed ten barely resurgent ferns, at Ground Zero and to the south.   I will add these to my weekly rephotography round.  Perhaps some will survive the summer drought.

In this region there are perhaps 500 or 1000 dead crowns, like the one pictured below - a state they reach  roughly  two years after die-off.   The appearance of these few sprouting fronds might be explained by, or at least is consistent with, this model:

1.  The die-off is an epidemic event: a widespread occurrence at a particular time
2.  Some individuals (~2%?) though severely affected, previously judged dead, remain vital, making new small fronds, late in the season, several years after the initial infection.  That this spring has been long-lived, cool and with some rain, may contribute to this phenomenon.  I have noticed only a very few of these tiny sprouts in past years.
3. The hypothetical infection may be cyclical.  Weak support for that possibility is provided by old stubbled fern crowns to the south of Ground Zero which we estimate (without metrics or dependable assays) to  be from about 20 years ago.

Port Ludlow Die-Off History 2008 - present

From:  Ellen Theisen and Ken Thompson 

We are writing to you in the hopes that you have discovered a remedy for the sword fern die-off, and to share with you some information about our experience and experiments, since we were the first to report the die-off to Jenny Glass and Olaf Ribeiro. 

We recently found your blog about the Seward Park sword fern die-off. For 10 years, we have been concerned about the die-off on and around our property, but until now, we didn't know of any others who shared our concern.

1990. The 2.5 acres of our land in Port Ludlow were covered with huge, gorgeous sword ferns, reaching up to nearly six feet high. The 160-acre forest surrounding us was also covered with big, healthy ferns.

2008. We began to notice that the ferns were dying in three or four areas of our property. Within a few years, an entire quarter acre held only dead fern root balls, and no weeds at all, with half an acre more showing severe damage.

July 2013. The die-off had continued to grow with many ferns dying or looking unhealthy. We cleared out a forest of blackberries and salmonberries and discovered another quarter-acre of die-off we had not seen before. 

August 2013. We sent samples of some dead and dying fronds, along with a document of many annotated photos, to Jenny Glass and Marianne Powell at the WSU extension, asking for a diagnosis. They responded that the cause was unknown, and that neither they nor other plant specialists at WSU had heard of any similar problem elsewhere.

April 2014. We contacted Olaf Ribeiro. He examined the ferns, and took soil samples to analyze. He found evidence of a spider-mite infestation, but he said that he had not seen this sword fern die-off anywhere else. We cleared up the spider mites by spraying with CG-Mite.

May 2014. We applied organic products that strengthen roots and kill fungus to the soil around approximately 1000 healthy, dying, and dead ferns. 

April 2015. We repeated the application. We also transplanted 34 ferns into a 1000 square-foot die-off area, and they are still alive and doing fairly well. 

2017. We transplanted 8 ferns into another 400-square-foot area, and they have grown fiddlebacks this spring, and most of them look healthy. 

Current. We have seen signs of improvement. Ferns are even beginning to grow in the first die-back area we observed.  However, an occasional fern still dies or looks unhealthy, and the 160-acre forest surrounding us is showing signs of severe die off. The 10 acres we have walked through are full of dead and dying ferns.

If you find any solution to the die-off, please let us know as soon as possible. We will, of course, be watching your blog and would be happy to send you any of our documentation.