Among the romantic images of the deep south are splaying live oak limbs covered with Resurrection Fern (Pleopeltis [old name was Polypodium] polypodioides), emerald green bunches of tightly clustered fronds.
Resurrection Ferns are epiphytes (=air plants), so called because they grow on other plants (most often Live Oaks and Cypress). They have running rhizomes that creep along the tree’s branches, with fronds sprouting along the way. They gather their nutrition from dust and other organics that settle on the branches, and their water is absorbed from the tree’s surface and the humidity in the air.
Since the symbiotic relationship between the fern and its host tree results in the fern benefiting (a place to live, gaining nourishment from elements collecting and moving along the tree’s bark) while the host is not affected at all, the relationship is called commensalism (if the fern benefited and the host was damaged, the relationship would be called parasitism; if both benefited, it would be mutualism).
During moist weather, Resurrection Ferns are open in full glory. On older trees, they can appear so dense that one expects the limb to collapse. However, huge clusters are quite light since there is no significant weight to their network of thin roots that snake through the rough bark substrate.
As the air dries due to the lack of rain, the fronds appear to shrivel and die as they turn brown and curl. This is a near perfect adaptation to conserve vital moisture during otherwise taxing periods of drought. The visual affect is strikingly different from the lush green growths that are customary in south Louisiana’s normally humid weather. But, all it takes is a nice rain and the fronds reabsorb water, slowly regain their deep green coloration, and uncurl to their customary flat fronds. Of course, this is the origin of the name – the seemingly dead fronds appear to come back to life.
Since they grow on limbs and trunks, their niche is characterized by light filtered through the host tree’s canopy.
As other ferns, Resurrection Ferns reproduce by spores which are produced in sporangia. Clusters of sporangia appear as small dark dots called sori that line the lower surface edges of the fronds.
Resurrection ferns are one of the few larger plants that have traveled to outer space during experiments on their abilities to perform under weightless conditions.
The next time you see Resurrection Ferns, you should see them both as a beautiful plant and as a species with exceptional adaptations for living in an environment with huge swings in rain and humidity.