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Vascular Plants of the Gorge at
Buttermilk Falls State Park (Ithaca, NY)

** Plant Finder **
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.About Ferns

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     If you've been studying ferns for a long time, and are comfortable with the terminology used to describe ferns, you may want to start using the key now. Just click the link above.  For everyone else, it is recommended that you review the material below.

For fern scientific morphology terms, click here.

      Of all the plant species found during this survey at Buttermilk Falls State Park, the ferns are the only plants that don't reproduce by seed.  They don't produce flowers either.  Instead, their reproductive process begins with spores, which disperse by wind from the parent plants, and continue their development by means of a multi-phased process.

     Fern leaves are also referred to as fronds in scientific literature.  Each fern frond is borne on a stalk called a stipe:  the equivalent to a leaf stalk for a tree, shrub or other type of herbacious plants.
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     For some species of ferns, fertile and sterile leaves look very different. (Refer to Figure B. above.) For most of our ferns, however, fertile and sterile leaves can be distinguished mainly by checking the undersides of the leaves. Leaves lacking spores on the underside would be considered sterile, although freshly emerged leaves of those species may, in some cases, become fertile later in the season.

    This key will begin by asking you to describe the shape of the leaves of the fern you want to identify.  What do we mean by "shape"?  Imagine viewing a leaf as a silhoette, focusing on the perimeter of the leaf and ignoring, temporarily, what is within the perimeter.  For example, is the leaf round, egg-shaped, oval shaped, very narrow and long, triangle-shaped or lance-shaped?  Let's look at few examples.

Figure C.  Egg-shaped silhouette of a black birch leaf.

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     Figure C shows a black and white image of a black birch leaf.  Of course, none of our ferns have a leaf that looks like this.  But it is an example of a very simple leaf outline:  egg- shaped.  For the first two decision points in the key, we won't be concerned about the other characters of a leaf, such as type of veins or whether the leaf has hairs.

     Later, the key will ask you about those other characters; most importantly, whether the leaf is divided into primary and/or secondary "segments".  Such leaves are called compound leaves. That simply means that the outline of the leaf is cleft multiple times into segments, analogous to cutting a pie into slices. Thus, the leaves of the polypody fern shown in Figure A above are cleft into one series of primary segments.  Most of our ferns have leaves that are compound leaves.  Shown in Figure D (below) are illustrations of three common types of fern leaf outlines.

Note also that the tissues of the individual segments are not joined together.  That is, the segments are distinct from each other, separated by a gap or recess, which is called a sinus.  This leaf is an example of a compound leaf that is "divided" ( cleft) once.  The edges of most of the segments of this specimen are also coarsely toothed.  Now, if instead of teeth, the edges of the segments had deep sinuses that extended more than half way to the midvein of the segment, we could say that the leaf was twice compound.  In other words, the primary segments would also be divided into smaller secondary segments.

Figure F.  Twice compound fern leaf example: marginal woodfern. ( Dryopteris.marginalis )

Figure G.  Three times compound leaf example of intermediate woodfern. ( Dryopteris intermedia )

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Images and text copyright  Arieh Tal, 2017-2022.  All rights reserved.  ( Terms of Use )