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  Nature Elective


Ferns
First posted June 26, 2004 Last updated August 1, 2004

There are seven species of ferns in the Cazadero region. Two are easily seen at camp: bracken ferns (above, left) and sword ferns (above, right). Three others can be found if you know where to look: goldenback ferns, five-finger fern, and woodwardia (chain) ferns. The final two, California polypody and Maidenhair, are in the Cazadero region but we have not yet found them in camp. (If you want to know more about ferns and their allies, the horsetails, in relation to other land plants, see Land Plants.)

Introduction

"Ferns make up one of the most popular groups of plants, exhibiting a tremendous variety of forms, shapes and unique life cycles. Approximately 11,000 species of true ferns have been classified (in comparison with the more than 325,000 species of seed-bearing plants)." (Michael Wood & Jake Sigg, Ferns of San Francisco)

Ferns are land plants with a vascular system (mosses and their allies do not have a vascular system*). Ferns do not produce seeds (like conifers) or flowers (like the flowering plants). They reproduce asexually by spores, which are borne in sori (seen in photograph at right, and enlarged, below) on the undersurface of mature leaves. They have a very complex life cycle, with an alternating gametophyte generation and a sporophyte generation; the fern that we are used to seeing is the sporophyte generation.

*As we saw in the section on Land Plants, the vascular system is an internal circulatory system of specialized tissues grouped as bundles in the roots, stems, and leaves of the plant. One of these specialized tissues is called the xylem, which transports water from the roots to the leaves, while the other, the phloem, transports nutrients and hormones within the plant.

Sori are the golden-colored dots on the underside of this sword fern leaf, taken at Camp on June 22, 2004. They are seen enlarged below.
Structure of a Fern
Spore-producing ferns (the one we usually see) are asexual and consist of an underground rootstalk called a rhizome, from which arise the roots. The rhizomes spread underground, growing continually. They send up the parts of the fern that we normally see. The stalk (stem) is the upright support for the fern, from which come fronds. We might think of these as the leaves, but they are different in structure from the leaf of a flowering plant. The fronds often consist of leaflets referred to as pinna (plural is pinnae). They arise from the rachis. The frond can be as above, and is called pinnately compound (sword fern, California polypody). If the frond has smaller rachae coming off it, with the pinnae directly attached to this secondary rachis, they are called twice pinnately compound (bracken fern, woodwardia fern). For another example, see this print.

Spores

Spores are fascinating. They are single cells that are very resistant to drying out. A spore is similar to a seed, in that it is structure used for propagation designed to withstand drying out. It is different in that a seed is an embryo (small version of the adult organism) that is multicellular and has stored food for the nourishment of the embryo. The spore is not a miniature fern waiting to sprout, but a plant part that has only half the full complement of chromosomes that will grow into another life form called a gametophyte, which will ultimately generate the sperm and egg that will unite to form a diploid (normal number of chromosomes) fern. The spores are contained in sporangia, which are grouped together into sore. You can see the sori at the right, on the undersurface of the fronds. For more details, see life cycle of a fern.


Fern fronds grow out from the base in the curled shape as shown at right. Can you guess what it is called?

A fiddleneck, and you can see why, compared to a sideview of the neck of a violin (fiddle is just a nickname for a violin, it is the same instrument; the music is different, not the instrument).

A new fern frond grows out as a curled growth called a fiddleneck.

A violin neck, as seen from the side, in a photograph by Vincent Oliver.

Fiddleneck unfurling into a new frond
Photo by David Nelson, July 23, 2004, in Marin

Ferns of Cazadero

Sword Fern Polystichum munitum

The most common fern you will see at Camp is the sword fern, also called the western sword fern. It is very widely distributed, found in every county in California that borders the coast, from northern border to the southern border of the state, and in many inland counties. It is so common within the redwood forest, it has been said that if there is a tree overhead, there is a sword fern underfoot. It has a simply pinnated leaf, which means the pinnae come off the central stem of the frond. Compare this to the bracken fern, below. It is about 2 to 4 feet in height.

It is very easy to grow, making it ideal for ornamental gardens, if you want to put a bit of Caz in your life. They can be purchased at many commercial nurseries.

Sword fern is common throughout Camp.
(photographed at Caz on June 22, 2004)



Bracken Fern
Pteridium aquilinum

Bracken ferns can be seen where it is just a bit dryer than the areas that support sword ferns. They can be seen just above Austin Creek Road, the road above Camp. A separate page is devoted to the bracken fern. It has a double compound leaf, which means that each frond stem has a second stem branching off of it, to which the pinnae are attached.

Bracken fern at Cazadero


Goldenback Fern
Pityrogramma triangularis

This is a delicate, 1 to 4 inch tall fern that grows in moist, shaded, and protected places. The fronds explain its species name quite easily.

It might look superficially like a bracken fern in a photograph, but it is quite different in the forest. Besides its diminutive size, its fronds are simpy pinnate at the tip, but are secondarily pinnate at the base. The most distinguishing feature, however, is the back of the frond: it is a beautiful golden color (see next section).


A goldenback fern, photographed April 24, 2004, in the shade of an old redwood log, just downstream of the baseball diamond.
Although the fern is quite green on the upper side, the undersurface of the frond is quite pale, almost white, early in the year, turning a more brown shade later, and finally, as the sori mature, turns quite golden, as you can see here (photo from California Biota, by Luis A. Solorzano and Warren E. Savary). The beauty of this fern is well worth the effort to search it out.
Goldenback ferns dry out early in the summer, as can be seen above. These photographs were taken on April 24, 2004 (left) and on June 20, 2004 (right). The right photo was taken just a bit to the right of the left one. On the later photograph, the large goldenback fern on the left has begun to dry out and curl, while the smaller ones to the right are still green.

California Polypody
Polypodium californicum

This 6 inch fern can grow on almost anything as long as it is vertical: rotting logs, rock faces, even on the bark of living trees. It often grows in large colonies (see photo at right), and tolerates more sun than most of our ferns. Note the simple leaf structure (pinnately compound), as opposed to the bracken and goldenback ferns. One of its distinguishing features is the rounded tip of the pinna, which can be seen below. It derives its name from the Greek words polys, meaning many, and podi, meaning foot, because of the many knobby branches of the rhizome.

It is in the Caz region in many sheltered creeks, but is not now known to be in Camp itself.


This group of polypody was photographed
Jan 19, 2004, in Muir Woods.

Polypody growing on a steep rockface.

Western Chain Fern
Woodwardia fimbriata

This is our largest fern, easily growing to 6 feet and can be as tall as 9 feet in ideal environments. It can be found along the Austin Creek Road, in among some bracken ferns, just upstream of camp.

The name comes from the elongated sori, which are arranged in two rows, along each side of the midrib, that look like a chain (photo by Sue Mandeville).

Western chain fern, photograpy by John Dove.


Five-Finger Fern
Adiantum pedatum

The delicate five-finger fern grows usually to about 6 inches, although 10 inch specimens can be found. It grows on heavily shaded steep walls of creeks or seeps. This is a five-fingered fern, photographed in the creek below CazSonoma Inn, which is located downstream from Camp, on Kidd Creek, a little tributary of Austin Creek, on June 24, 2004.

Five-finger ferns are rare in camp, found so far only in one place along Austin Creek and in one tributary. Look on the main camp side of the creek, about half-way upstream from the footbridge to the entrance of the small creek at the upstream end of Camp. You can also find one group up this creek, on the downhill side, about 25 feet from Austin Creek at summer level. Please: don't pick or hurt these, or we will lose our only specimens.

Maidenhair Fern
Adiantum capillus-veneris

The delicate maidenhair fern is somewhat similar in habitat, size, and growth form as the five-finger fern. It grows usually to about 10 inches, although 18 inch specimens can be found. It grows on heavily shaded steep walls of creeks or seeps.

We have not yet found it in camp, but it is normally found in redwood forests along streams or creeks. We will keep looking!

See the CalFlora listing.

This maidenhair fern was photographed in Samuel P. Taylor State Park, which is located in a redwood forest in Marin County, on the was out to Point Reyes. Photograph by David Nelson, August 1, 2004.

 

References

The San Francisco State Department of Geology has a great section on sword ferns.
The USGS has a section on ferns and their allies, with good photographs.
The American Fern Society has a website.

Acknowledgments

The material above was based on Plants of the Coast Redwood Region, by Lyons and Cuneo-Lazaneo. Additional material is based on the San Francisco State Department of Geology has a great section on sword ferns. The first two sentences of the Introduction are by Michael Wood & Jake Sigg, and are from their webpage, part of the Yerba Buena (San Francisco) chapter of the California Native Plant Society.
The sword fern fiddleneck is used with permission and was taken by Charles Webber; it is © California Academy of Sciences. The violin fiddleneck is from the instructional manual for PaintshopPro. The illustration of the parts of a fern are from my old nature reference, Sierra Nevada Natural History, published in 1966! It is by Storer and Usinger. I used this book when I was a nature counselor at the San Jose Family Camp, in 1969-72, where I was christened with my camp name, Bugs, that I still use at Caz. The goldenback fern underside is from California Biota, by Luis A. Solorzano and Warren E. Savary. The California Polypody is from the Mostly Natives Nursery, in Marin; the sori of the polypody is from the Marin Chapter of the California Native Plants Society. The woodwardia sori are by Sue Mandeville, from the Hardy Fern Foundation; the frond was from the Pacific Rim Native Plant Nursery and is by John Dove.