Adder's Tongue Fern

Adder’s Tongue Fern is one of those low growing plants that is inconspicuous to the casual observer. It’s usually surrounded by other non-descript plants that blend into a bright green ground cover. I make a point of looking for it each spring.

This is Ophioglossum vulgatum, although positive identification of this genus can cause a certain amount of frustration. Different sources rely on varying descriptions of physical characteristics when describing the different species. In particular, I’m certain that I have Ophioglossum vulgatum, but I’m not sure that I don’t also have the rarer Opioglossum engelmannii.

There is a wide variation of leaf shape within each population of plants I examine. Leaves might be short and broad with a rounded tip or long and narrow with a pointed tip or wide with a blunt tip with a tiny spur. Some leaves have a central crease while others don’t. Some curl forwards on the sides and others arch backwards. There can be a whole range of shapes and sizes all in the same patch of plants. Trying to match physical characteristics to written descriptions can be very frustrating.

One characteristic that is supposed to be definitive for identification purposes is the pattern of leaf venation. You can see that this thick, fleshy leaf does not easily divulge the secrets of its veins.

I picked a couple of leaves and treated them to an alcohol bath to remove the chlorophyll. It turns out that venation can also vary greatly within an individual leaf. For the most part, the veins tended to match the patterns illustrated for vulgatum. When the plant nears the end of its season, I may do a more extensive collection of leaves and check venation. Collecting leaves late in the season should reduce stress on the plants donating to the collection.

I originally found these ferns growing in the old fence rows. Through the years I have seen a rapid increase of plants showing up in the fields. Most of the plants are found in dry, calcareous areas that more match the preferred habitat of engelmannii, so this adds to the feeling that this rarer species might also inhabit Blue Jay Barrens.

When you don’t have time to do extensive flora surveys of an area, you sometimes wonder if your casual observations of plant population increases might not be totally accurate. This plant, growing in the middle of one of the old crop fields, confirms that my observations are correct. Prior to 1985, plowing and chemical applications to this field would have made the existence of this plant impossible. This plant has to have arrived here after my management activities began.

It’s not just one plant showing up in the field that gives me confirmation. This whole area now supports hundreds of Adder’s Tongue Ferns living among the Indian Grass. Regardless of the species, I enjoy having this plant as a part of the Blue Jay Barrens flora.