Sori are a fern's spore clusters

Fern Identification ​in the Pacific Northwest

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If you live in the Pacific Northwest and struggle with fern identification, you aren’t alone. The PNW has a lot of ferns. They are moisture-loving plants, and, well, we have a lot of moisture here. One of my first videos was all about IDing fiddleheads, but after the video came out, it became apparent that some fern ID might come in handy. I’m going to cover the most common ferns in the Pacific Northwest (well, at least on the Candian side). There are quite a few, but I’ll stick to the most common six: sword fern, deer fern, licorice fern, lady fern, spiny wood fern, and bracken fern.

First, Fern Identification Definitions

Fern Parts
Image Source: Hallowell and Hallowell (see below)

The first step to fern ID is to know what the heck your field guide is talking about.

Leaf/Frond:  The whole frond of a fern is called the leaf.

Leaflet/Pinna: These branch right off the stem.  You might be tempted to call them a leaf.

Lobe/Pinnule: Not all fern have this. They branch off of the leaflet.

Pinnate: This is the number of times a leaf branches. For example, a sword fern would be once pinnate, because the leaflets that branch from the stem are solid, with nothing branching off of them. The fern in the diagram to the left would be twice pinnate.

Scales:  The paper-like scaly bits at the bottom of the fern.

Sori:  The little clusters of spores on the undersides of leaflets.  I mention them mostly because in the video, I was calling the scales the sori.  Turns out I’ve been calling them the wrong thing for half my life. Oops.

Sori are a fern's spore clusters
The sori are the clusters of spores on the underside of the pinna. Photo Credit: Jim Conrad.

Sword Fern (Polystichum munitum)

Sword Fern -  Polystichum munitum
Photo credit: Krzysztof Ziarnek, Kenraiz (See below)

Sword fern is by far the most common fern around here.  Its waxy leaves don’t rot over winter, leaving the old fronds from last year battered and clinging to life.  We can think of it as the obnoxious slob of the fern world.

The main feature you need to know is that it is once pinnate and generally large (up to 1.5 m) with plenty of scales.  In summer, the clusters of spores on the undersides of leaflets are easy to find.

The other once pinnate ferns in the area (deer fern and licorice fern) have a few differences.  I’ll get to them in a minute.  The scales of this fern make it unpleasant to eat as a fiddlehead.

Deer Fern (Blechnum spicant)

Deer Fern - Blechnum Spicant
Deer ferns have male fronds (standing straight up) and female fronds (fuller and lower to the ground)

Deer fern can look a lot like a small sword fern to the untrained eye, but there is one significant difference…at least in the summer – they produce two types of fronds.  The female ones resemble those of sword fern but are generally narrower and less battered looking.  They stick around all winter, but unlike sword fern fronds, never produce spores.  The spore making is up to the fertile (male) fronds, which stick straight up with skinny little leaflets poking out of the stem. Their undersides will be covered in spores.

The fertile fronds are only around in summer, so if you are IDing ferns in the winter, take time to compare the plants.  The deer fern is smaller and the fronds are shaped more like a feather, whereas the sword fern fronds are more triangle shaped. The sword fern also often looks messier.

Licorice Fern (Polypodium glycyrrhiza)

Licorice fern - Polypodium glycyrrhiza
Licorice fern growing on mossy maple. Photo Credit: Alanah Nasadyk (see below )

Licorice fern is only once pinnate so could be confused with sword fern, but it is much smaller, and usually grows as a single frond, or a group of single fronds, rather than in a bunch. It stays green all year round.

The real distinguishing factor for licorice fern is where it grows. It is an epiphyte, meaning it grows on other plants without being parasitic. It loves the moss covered tree of the PNW and can often be found on mossy maples.

Another way to distinguish it from others – pick a frond and bite the base.  It should taste a little like licorice.  Bite the rhizome (root) and it should taste overwhelming so.  None of the ferns around here are particularly toxic, so it won’t kill you if you get it wrong.  It seems to grow better during the cooler months, and starts to die back at the end of summer as things get dryer.

Lady Fern (Athyrium felixfemina)

lady fern - Athyrium filix-femina
Lady fern. Photo Source: Barry Breckling, US Forest Service (see below)

I would hazard to call this the second most common fern in these parts, often growing alongside sword fern.  True to its name, lady fern is the daintiest of the bunch, though it can grow to a hefty 2 m.  Old fronds from the year before tend to rot before the next batch come out.  The leaves are 2-3 time pinnate and much softer than the other ferns.  The leaflets are smaller at the top and bottom, making them somewhat feather shaped.  The leaflets tend to start fairly close to the ground and the scales at the base are less prominent than the similar looking spiny woods fern (see image below).  Lady fern is the most edible fiddlehead in the PNW.

Spiny Wood Fern (Dryopteris expansa)

Spiny wood fern dryopteris expansa
Spiny wood fern. Image Source: US Forest Service

It’s easy to mistake a spiny wood fern with a lady fern, especially a young lady fern. There are some key differences though.  The leaflets typically start further up the stem, and the bottom ones are the longest.  The result is the frond looking more like a triangle…so they look a little spiny…get it?  They also have more scales around their base, another feature that makes them a little spiny.  Besides that, they are often smaller, growing in poorer soil than lady fern, often on rotted logs.  This is not always a great indicator though, because they often grow right beside lady fern.

Spiny wood fern (left) has many brown papery scales at its base, considerable less than lady fern (right).  Lady fern stems will also be thicker and lighter in colour.

The rhizomes were traditionally roasted and eaten as a starch. I gave it a try in the video below.

Bracken Fern (Pteridium aquilium)

Bracken Fern. Image Credit: Rasback (see below)

Folks often have trouble telling bracken fern apart from spiny woods fern and lady fern. The first thing I’ll say is that they tend to be bigger – up to 5 meters tall, in fact (but usually around 1 or 2).  They like meadows and clearings, rather than the dense forest that lady fern and spiny wood fern prefer.  The main difference that I use, however, the leaflets.  They appear to grow on a stem branching off from the main stem, whereas the leaflets of other ferns look a little more…umm…leafy.   If you were to cut one leaflet off, it would resemble an entire spiny wood fern frond.

There are other ferns around here, but they are generally smaller and less common, usually growing on cliff sides and out of the way places.  If you are really that into learning more, I would recommend  Lone Pine’s Plants of Coastal British Columbia.  It’ll do for you Washingtonians as well.

Clear as mud, right?  Now that you know some basic fern identification, it’s time to get out and harvest some fiddleheads. This is my first video ever made on my channel, but it still has some useful information.

Want more PNW foraging? Check our post on Easy Spring Foraging.

Favourite Plant Book

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Plants of Coastal British Columbia, J. Pojar, A. MacKinnon. Lone Pine Publishing.ISBN 1-55105-042-0

Most of the information here has come from my trusty Lone Pine. It is an excellent field guide complete not only with how to ID, but great ecological and anthropological information.

Photo Credits

Diagram: Illustration derived from Fern Finder: A Guide to Native Ferns of Central and Northeastern United States and Eastern Canada by Anne C. Hallowell and Barbara G. Hallowell, published by Nature Study Guild Publishers

Sori. Jim Conrad. Public Domain

Sword Fern by Krzysztof Ziarnek, Kenraiz [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons

Deer fern – public domain

Liquorice fern Alanah Nasadyk; https://www.flickr.com/photos/146378829@N04/31719654226   [CC BY-SA 2.0 CC BY-SA 2.0  (https://creativecommons.org/licenses/by-sa/2.0)]

Lady fern by Barry Breckling.  Public Domain from US Forest Service

Spiny Wood Fern: Public domain from US Forest Service

Bracken Fern – Rasback; Rasbak [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons https://commons.wikimedia.org/wiki/File:Adelaarsvaren_plant_Pteridium_aquilinum.jpg)]

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