Pioneer Valley Fern Society

Winter Ferns

#2 Common Polypody

In looking back over the numerous news articles we have done on fern identification, I now see I have failed to include some of our most common ferns! After starting with Christmas Fern last month, we now move on to Common Polypody (Polypodium virginianum). It is one I expect most of you know, a good way to start the new year. It is the fern we find most often growing in semi-shady areas on exposed rocks in our region. Another name for it is Rock Polypody. They are leathery, evergreen, and grow in colonies.

We also have Appalachian Polypody in our area, but less common. I will highlight that one in another article. The Common Polypody is identified from the Appalachian by having a blade that is generally oblong or lance-shaped and widest in the middle, while the Applalachian is more triangular in shape, widest at the base.

They have beautiful large yellow to brown sori on most of the pinnae (leaflets), which can often be seen throughout the year. They can be differentiated from Christmas Ferns because the Polypody blades are "pinnatifid", meaning the blades are deeply lobed and cut almost to the rachis (stem) but remain attached to each other. The pinnae of the Christmas fern are attached separately to the rachis (and have shapes that may look like a Christmas stocking or sleigh sideways). Christmas Ferns also have different fertile fronds, which are taller than the sterile ones, with narrow brown tips of the blades.

Polypody is one of the 4 common ferns in our area that retain their green fronds through winter. The others are Christmas, Evergreen Wood Fern and Marginal Wood Fern. All may be found growing on rocks, but the others will also commonly grow on the forest floor. Polypody will usually only be found on rocks.