Most people love ferns in general, but many people do not separate the various fern species from the green blur of a lusciously green forest or bank. Around Humboldt Bay this is not hard to do. Here is a quick guide, starting with a species that is ending its year as most plants are quickening theirs.
By the end of May, when so many plants in our area are at the peak of green vigor, Roadbank Fern (Polypodium calirhiza) is yellowing and drying. It has dropped its spores, and will be dormant for the summer dry season. Soon after the first rains in fall, fresh, green fronds will emerge from its creeping, branching stem that clings to the steep road cuts, rocks, and dunes where it lives. Some sources call it Nested Polypody, a baffling name that conveys little information to most people. The identification of Roadbank Fern was confused with California Polypody (Polypodium californicum) until in 1991 a study of these species plus Licorice Fern (Polypodium glycyrrhiza) revealed that Roadbank Fern originated as a hybrid between California and Licorice Ferns, and is now hardier and more widespread than either of those. Licorice Fern is similar but with pointier leaflets and favors lusciously mossy trunks of deciduous trees like Big-leaf Maple, where it usually can stay green all year.
One more creeping fern found here is Leather Fern (Polypodium scouleri). Its fronds are darker green, tougher (leathery!), have a long, rounded lobe on the tip, and are evergreen. It grows as an epiphyte, including in the largest Redwoods, where its creeping stem and tough leaves create huge islands of soil in the treetops. A falling branch can carry with it a clump of Leather Fern, which will then grow on the forest floor.
The classic forest floor of Redwood forests is a lush covering of Sword Fern (Polystichum munitum). Its fronds are simply lobed, like the polypodies, but are arranged in a tuft that can grow very large. The leaflets are attached by just a corner to the leaf stalk and get gradually shorter toward the frond tip. Sword Fern is hardy; it grows in dry forests as well as damp ones.
Also in shady forests and with simply lobed fronds arranged in a tuft, is Deer Fern
(Struthiopteris spicant, formerly Blechnum spicant; its taxonomy has been updated).Often found on cut banks by a trail or road, Deer Fern is smaller and tidier than Sword Fern, with a circular crown of fronds and sometimes narrower, browner reproductive fronds standing vertical in the center. The entire leaflet base is attached to the leaf stalk, and the leaflets get smaller both toward the tip and toward the base.
A more “ferny” fern, with finely divided leaves in these shady forests is Spreading Wood Fern (Dryopteris expansa), usually found on rotting wood, like stumps, fallen trunks, or piles of shed bark at the base of a tree. Its fronds have a triangular outline, and it is evergreen. These features distinguish it from the similar Lady Fern (Athyrium felix-femina), common anywhere moisture is found, in forests or out. Its soft, bright green, finely divided fronds die every winter. Its fronds have a diamond-shape outline, with small leaflets at the bottom as well as the tip. A large Lady Fern may have a short trunk and a large, lush presence.
Five-finger Fern (Adiantum aleauticum) grows in damp but well drained, forested places,
like the walls of Fern Canyon or a shady curve in a forest trail. Its dainty leaflets on delicate, wiry, black leaf stalks are guaranteed to elicit oohs and aahs. These leaf stalks are an important ingredient of Native Californian baskets. Despite its delicate appearance, Five-finger Fern also grows in serpentine rock jumbles along sunny mountain roads.
A fun, little fern encountered in surprising places is another species with a wiry leaf stalk, Goldback Fern (Pentagramma triangularis). It can live in otherwise dry habitats, like under a large driftwood log at the back of the sandy beach or on the road bank in the dune forest. It deals with dry periods by curling up its fronds, waiting for rain. Its other surprise is the clear yellow color all over the backs of the triangular fronds.
The world’s most widespread fern is worth knowing. Bracken (Pteridium aquilinum), like
the polypodies, sends up single fronds from a creeping rhizome, but its rhizome is well underground. Its frond has a very tough leaf stem and is very “ferny.” It can be 1-8 ft tall and dies back for the winter. Bracken lives in both shady and sunny habitats. Its tough, brown, dry, old fronds betray its presence all year.
These ten ferns account for most of the ferns encountered in the coastal and Redwood zones of Humboldt County. They are an easy subset of our plant neighbors to get to know. Interested in learning more? Visit http://northcoastcnps.org/ to see when the next “Ferns in the Dunes” walk will be held.