Climbing Fern is an unusual plant found at a few locations on the Arboretum. It appears to be more of a vine than a fern. Its compound leaf (frond) consists of a twining, vine-like stalk (rachis) with sterile, palmate leaflets along its base and smaller fertile leaflets bearing sporangia toward its tip. The sterile leaflets (pinna) consist of a pair of palmate pinnules each of which has 5-10 lobes. These sterile pinna are evergreen and persist through the winter, while the fertile pinna die back. The climbing leaf can reach 3 meters in length. The genus Lygodium is mainly tropical, with L. palmatum being the only member native to North America. Two related species (L. japonicum and L. microphyllum) have been introduced into the southern US and are considered invasive. Climbing Fern is found throughout the eastern US, ranging from New England south to Florida, and west to the Mississippi River and Michigan's Upper Peninsula. It is locally rare in most areas, but may be most abundant on the Cumberland Plateau. In the past it was collected extensively for Christmas decorations in New England and is considered a species requiring protection in many states.

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