Pleopeltis polypodioides (Polypodiaceae) Resurrection fern (Polypody family)
Origin: Subtropical Americas, including the SE United States; Africa
Florida is home to dozens of species of epiphytic plants, mostly orchids, bromeliads, and ferns. The most common epiphytic fern in the Sarasota area, and perhaps the most interesting, is Pleopeltis polypodioides, also known as resurrection fern. It gets its common name from the fact that during dry spells, the fronds can lose almost all of their stored water, appearing completely desiccated, and then after a good rain “come back to life” again. Of the three more common epiphytic ferns in our area, resurrection fern is also unique in that it prefers the craggy bark of live oak limbs as a host rather than the soft boots of cabbage palms, which the golden polypody and shoestring ferns seem more attracted to. Resurrection fern will oftentimes be spotted growing alongside Encyclia orchids and Tillandsia species.
When the fronds curl during a dry period, they curl inward so that the sori (the spores) of the fern are facing up. Not only does this cause the plant to look even more brown and dead, as the spores are a brown-orange color, but it also allows the plant to regenerate as quickly as possible in a rain, as the underside of the frond is more adapted to absorbing water than the glossy top. Pleopeltis polypodioides is also a great “indicator plant” when it comes to rainfall; Florida is notorious for receiving spotty rain coverage during the year, and it can be difficult to know if an area has received a lot of rain, even if one knows that an area right next to it has. If there is Pleopeltis present, however, one need not guess; depending on the state of desiccation of the fern’s fronds, a good assessment of recent precipitation can be made. When an area has been receiving regular rain and humidity, the resurrection fern will be deep green and lush, blanketing oak limbs like a thick carpet. During dry spells, the fern really does look dead.
Resurrection fern plays a very important role as a micro-climate modulator of our epiphytic gardens in the trees. Once a patch of ferns has established on a limb, it becomes a “trash collector” of sorts, catching leaf litter and other debris which would usually be blown to the forest floor. Even during dry spells, when the ferns are desiccated, the biomass itself, along with the leaf litter it has trapped can hold enough water to allow other plants, such as orchids and tillandsias, a chance to germinate and grow to adulthood. Just that small amount of trapped, moist organic material can increase the humidity of the area directly around it enough to provide better conditions for future epiphytic growth. The fern’s rhizome, which creeps along the host tree’s stem, also prevents “erosion” from wind and hard rain that a bare tree branch would be subject to, sheltering epiphyte seeds and seedlings, especially on our more smooth-barked tree species, such as maples.
Here at the Marie Selby Botanical Gardens, we have resurrection fern growing in most of the native oaks on campus, as well as in many exotic species of trees and shrubs. Depending on recent rain conditions and irrigation (some of our gardens are heavily irrigated and some receive no supplemental irrigation,) there is an opportunity here to observe the fern in both stages of growth, desiccated and lush, in the same day.
Text by David Troxell