The Amazing Sword Fern

The Amazing Sword Fern

by Brian Bodenbach

One day in the early 1990s, I was checking out a recently completed stream restoration with a fisheries biologist who had participated in the project. At the time, large-scale restoration projects were just becoming common in our region. He asked for my opinion on which native understory plant is best for erosion and runoff control.

Sword fern 2 (003)

“On a watershed scale–hands down–the Sword Fern!” I emphatically replied. He looked a bit perplexed. I think that he expected me to name any of a number of deciduous shrubs–Red-osier Dogwood (Cornus sericea), Salmonberry (Rubus spectabilus) , Snowberry (Symphoricarpos albus), etcetera–that had quickly become popular among restoration designers. Deciduous shrubs like these made up the majority (and often still do) of plantings in restoration projects. On one hand, this makes sense; many of these native shrubs grow and establish quickly, and some spread to form dense thickets. This has big advantages in the short term as a large area can quickly become re-vegetated. But in the long run I think this actually becomes detrimental to the goal of many restoration projects: bringing the land back to being a coniferous-dominated forest–one of the planet’s most biologically rich landscapes. And in our region, beneath that canopy of big conifer trees –Douglas Fir (Pseudotsuga menziesii), Western Hemlock (Tsuga heterophylla), Western Red Cedar (Thuja plicata)–there is often a shrub and groundcover layer built on a foundation of Sword Fern.

As in many design fields, Landscape Design observes a rule of thumb: Form Follows Function. Whether I am designing/installing a backyard landscape or large restoration project, or maintaining an existing landscape, the same questions always come to mind: How can I take the water falling from the sky and the building downspouts and a) use it to nourish the plants and b) put the rest into the ground to slowly feed into the local stream and benefit the salmon? How to maximize the habitat potential of a little corner of a small yard to provide cover and food for birds, pollinators and other wildlife? How to delineate a large restoration area into zones: one for wildlife that prefer deep forest, one for open-land dwellers, and additional zones for streamside and wetland areas? And how to accomplish all this in a way that feels natural and looks beautiful? Anchoring all of this is my personal palette of plants that serve multiple functions to meet those objectives. Front and center on that palette is the Sword Fern.

Sword fern 1

Why is the Sword Fern so important? For starters, the Sword Fern is evergreen; it retains its foliage year-round. This is a big deal. In a part of the country where eighty percent of annual precipitation comes in the form of rain falling during the “winter months”—from October into May, having evergreen foliage means there is something to break the force of rain before it hits the ground. Especially when one looks at an entire hillside covered with Sword Ferns, it’s easy to see that this goes a long way towards preventing erosion and controlling runoff. Also, the foliage of evergreen plants tends to take longer to decompose. I have read that Sword Ferns fronds can take up to seven years to totally decompose (although my own observations around greater Seattle seem more like three or four). Contrast this with deciduous plants, the ground under which can go from a layer of leaves in fall to almost bare dirt by the end of the following summer. Again, big implications for erosion and runoff.

Sword Fern creates habitat. The buildup of fronds in varying stages of decay forms a ‘skirt’ around its base which creates cover for wildlife. I find more amphibians (frogs, salamanders etc.) hunkered down in the dense duff surrounding Sword Ferns than anywhere else. State biologist Marc Hayes tells me there is a correlation between the presence of native amphibians in Sword Fern duff (e.g. the Northern Red-legged Frog, in steep decline around here) and mollusks (slugs and snails), some of their favorite food. I suspect this dense duff also helps with thermoregulation (the ability to avoid the extremes of winter cold and summer heat).

And those roots! Sword Fern roots grow into a dense fibrous mass that can extend down as deep as two feet. This root mass does a great job of locking up the critical life-giving humus/high organic soil layer that feeds the landscape and to which the Sword Fern contributes with its accumulation of slowly decomposing fronds. The so-called “gardeners gold” in my world. Early in my landscape career, when given the opportunity to rescue Sword Ferns from an impending development site, I would always try to get as large a root ball as possible when digging mature plants from the ground to lessen transplant shock. This sometimes meant muscling 150-pound plants out of the ground and into the truck. And I knew that I hadn’t even gotten the entire root ball. It didn’t take long for my body to let me know this wasn’t that great an idea! From a business perspective, the amount of time and effort it took convinced that young knuckle-headed landscaper that purchasing nursery-grown potted ferns was the better way to go.

Early this year, Shirley and I attended a Native Plant Society meeting on a mysterious Sword Fern die-off* that has been noticed in several areas including Seward Park in Seattle. One of the things we learned is that there is some evidence that Sword Ferns can have a very long lifespan; one fern expert said they may live as long as 1,000 years! I was not surprised to hear this. I believe this is true of many understory plants in a stable, forested landscape. The die-offs are something that really concern me since I recognized long ago the critical role this one plant species plays in maintaining a healthy coastal northwest ecosystem. The cause of the die-offs has not been discovered, but some think climate change may play a role. Fortunately, some of the areas experiencing die-offs have been replanted with some success. What the future holds in a world with a rapidly changing climate, no one knows for sure.

What follows may seem a little romanticized, but for me this is true. To many, the Sword Fern is so ubiquitous on the northwest landscape as to almost escape notice. What I see though is the workhorse of the watershed. When I look at forested hillsides carpeted with Sword Ferns, or pay attention to the here-and-there patches I have planted in our yard over the years, I see red legged frogs. I see stable slopes. At the foot of a slope, I see spawning salmon thrashing in their natal stream. I see a winter wren hopping on a log and scooting among the fern fronds, its beautiful song in counterpoint with the soft pitter-patter of winter rain falling on fern fronds. I hear an unseen Swainson’s Thrush calling under the canopy of the cathedral forest. Form follows function.

*3 web links to info on mysterious Sword Fern die-off: Seattle Times, a blog about Seward Park’s Sword Ferns, Tim Billo presentation


Brian Bodenbach (Biosphere Landscaping) has been an important contributor in many ways to Tadpole Haven’s success. His practical skills are very handy, but his knowledge of native plants, ecosystems and restorative landscaping is invaluable.

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