Southern Grape Ferns (Sceptridium biternatum) are common in moist forests throughout the Piedmont of North Carolina. They are small ferns, usually 3 to 6 inches across, and have a fleshy, succulent texture. They are members of the Adder’s Tongue family (the Ophioglossaceae), which is sometimes referred to as a family of succulent ferns. Until fairly recently, they were classified as Botrychium biternatum, and the new genus name of Sceptridium has been slow to be recognized.
Southern Grape Ferns emerge in the summer and early fall, and remain throughout the winter. Pictured below is the typical form most frequently seen on the forest floor.
They often appear in small clusters, as illustrated below.
Southern Grape Ferns are variable in color, shape and size. An individual with a yellow tinge is shown below.
In the fall, fertile fronds arise from the base. A frond is the leaf of a fern, and a fertile frond is a highly specialized frond that differs markedly in form and size, and carries the sporangia. The sporangia are the cases or capsules that bear the spores of the fern.
Below is a closer look at a fertile frond bearing sporangia. The shape of the fertile frond is said to resemble a king’s scepter, which gave rise to the genus name Sceptridium.
Below is a closer look at the golden sporangia. Their resemblance to clusters of grapes is the source of the common name Grape Fern.
Sceptridium dissectum – the Cut-leaf Grape Fern – is a close relative of the Southern Grape Fern, and is rare in Central North Carolina. It was also classified as a Botrychium until recently and was considered a form of the Southern Grape Fern. It has now been moved into its own separate genus and species. The fronds of this species are divided for a third time, creating a fragile, lace-like appearance, making it easily distinguishable from the Southern Grape Fern, whose fronds are twice divided.
There are two forms of the Cut-leaf Grape Fern; one of them complicates field identification. Forma dissectum is the rare one illustrated by the two photos above. It is easily identified. Forma obliquum (not illustrated) is much more common and can closely resemble the Southern Grape Fern, leading to confusion. Perhaps the best way to be certain of identity is to look closely at the margins of the frond. The two close ups below show the sharply serrated margins of the fronds of Southern Grape Ferns. These serrations can be seen in the field without magnification.
The frond margins of both forms of the Cut-leaf Grape Fern are usually completely smooth or at most have indistinct or obscure serrations. The close up below shows the divisions of the frond, looking like jigsaw pieces, but the complex margins can be seen as completely smooth without serrations.
The Southern Grape Fern (Sceptridium biternatum) can also be confused with the Rattlesnake Fern (Botrypus virginianum) which has a very similar form and appearance. There is a simple way to distinguish them.
The Rattlesnake Fern is deciduous and the Southern Grape Fern is evergreen. The Rattlesnake Fern arises in the spring and is gone by late summer and fall. The Southern Grape Fern arises in the summer and fall, and remains throughout the winter.