A Sight for Sori: Discovering California's Native Ferns

Tapestry of ferns, moss and wildflowers along the trail at Pinnacles National Park

For most of my life my association with ferns has been one of caretaker and houseplant. That relationship has been replete with drama with certain favorites---rabbit's foot fern, maidenhair---refusing to thrive under my care regardless of my dedication to meeting their needs. Or, if they find a spot that pleases them, expressing their displeasure with a change of venue by an initial drop of frond that inevitably leads to a catastrophic collapse. In my near half a century of indoor gardening I have committed fern herbicide on an epic scale. Why have so many been sacrificed for my love? I think ferns simultaneously intrigue and soothe us, and that is an alluring combination.

Sorry, I hate this movie but this just works here.

Ferns evoke memories of tropical places in me. In some cases the memory rush is a short trip from my conscious mind---my tropical life phase in Hawaii or a childhood moment curled under the fronds of a tree fern in my backyard---but I think some memory is coded in my genes, the one that have carried my elements up from the Carboniferous Period, 350 million years ago: the age of ferns. This is old love.

Depiction of the Carboniferous at the Field Museum (photo fieldmuseum.org)

You may be surprised to know that California has a diverse array of native ferns. You have seen them, if you have hiked a trail through the redwoods or oaks, your brain decoding the feathery fronds into the category "fern" if only in the periphery of your awareness. Or, maybe you are a lover of house plants as I am, and your coding runs deeper: it's a maidenhair, or a sword fern. While Harry admires the great trees on our frequent strolls through the redwood groves crowning Monterey Bay, I have lately found myself stooping in admiration at every new fern species. You see, wild fern diversity is my latest discovery. In much the same way that birding first opened my eyes to the feathered ones as a teenager, phycology class at Oregon State inflamed my passion for algae and, most recently, the naming of butterflies elevated the "orange ones" and "yellow ones" to actual species, my fern universe has expanded and my consciousness will never be the same. I owe a good deal of my fern enlightenment to this $4 book, recommended to me by a fern expert:

If you'd like to know more ferns on a first name basis, I suggest this basic guide

On a recent hike in Santa Cruz I counted eight species, and those are only the ones I, as a novice, can identify. "We haven't seen that kind before!" I'd call to Harry, but he has no interest in a close inspection of the sporangia. As with most things in nature that we name and distinguish, each fern species has a unique set of characteristics that set it apart. If we are lucky (in that the species we want to identify has visible traits that can be distinguished in the field using our five unaided senses), and clever enough (in having a proper guide and knowing our fern parts), what was once a clump of fronds can now have a name. I find considerable satisfaction in that discovery.

Western sword fern, Polystichum munitum, from a newt's perspective

Five-fingered maidenhair fern, Adiantum aleuticum, amongst
the stream violets.

A wood fern, Dryopteris, reaches for the redwoods.

There are an array of new parts to learn, some of them familiar from phycology: not stem and leaf but stipe, frond, rachis, and pinnule. Rhizomes are the furry stems of ferns that give rise to common names like rabbit's foot and hare's paw. The key to unlocking a name may be on the underside of the frond where the spore-packed sori neatly sequester the fern's reproductive matters. Comments on my first fern observations on iNaturalist often suggested including a photo of the frond's underside, although at least one expert identified a species based on the imprint of the sori on the upper surface of the frond. But I am new to the fern puzzle and so struggle,"What the hell is the indusium?"

Wood ferns have distinctive sori lined up like cars in a parking lot

Bracken, Pteridium aquilinum, backs its sori up to the edge of each pinna

The glowing gold dust sori of the goldback fern, Pentogramma triangularis

If you're going to inspect the naughty bits of a fern, use care not to snap the stipe in the process! The spores grow into gametophytes (dig deep, back to biology class and the alteration of generations) which will produce eggs and sperm (yes, flagellate, motile sperm), which join to grow into the sporophyte, the familiar ferny part of the plant which produces the spores, and the whole thing starts over again. There is none of the bother of flowers and seeds. That swimming sperm needs a drop of water to make it's pilgrimage but ferns need not be limited to the moist tropics to thrive and can often do well (better than flowering plants in some cases) in marginal habitats by using alternative reproductive strategies that bypass the sperm entirely. I've spent a good deal of my life bypassing sperm, so I get it, ferns.

Ferns can be found along side the trail on many of my favorite hikes:

Coffee fern, Pellea andromedifolia, near the High Peaks at Pinnacles

Unfurling fiddlehead at Fremont Peak

Ladybug and bracken, Fremont Peak 

Fissure garden of Polypodium and lichen, Fremont Peak

Cheeky fern fists put 'em up at Manzanita Park

Bracken shadow play on the sand at Manzanita Park

Bracken lined trail---this species, while native, can be invasive

A search for ferns in Calflora brings up 95 results; some of these are endemic and rare and some are exotic and invasive. Some ferns are threatened by habitat destruction and poaching by rare plant collectors. Search for ferns in your neighborhood, admire them, maybe find their names, then leave them be to drop their millions of spores and carry on the alteration of generations. Taxonomy offers the naturalist the gift of diversity---suddenly the ferns are all around waiting to be noticed and named. They are more than a plant in a bathroom or greenery adorning a bouquet of the flowers they need not bear, but ambassadors of an ancient life form that has witnessed the births and extinctions of millenia. Take a deep breath and let the ferns tap into your inner Carboniferous.

The water fern, Azolla, shelters a Sierran treefrog, Pseudacris sierra.