When driving onto Jekyll Island, Ga. to visit my in-laws, I am greeted by huge live oak trees laden with Spanish moss which is like entering an enchanted forest. Just this year I was introduced to another plant commonly growing on the same live oak trees, the resurrection fern.
I wondered why these two plants thrive selectively on live oak trees but are harmless. The answer is fascinating.
First of all, Spanish moss is a flowering plant just like a lilac or daisy, not a moss at all. It reproduces by seed formation and by stem cuttings. It is rootless but contains the green pigment, chlorophyll, which starts the chemical reaction in a leaf to produce glucose for growth and reproduction. Spanish moss selectively grows on live oak trees native to southern United States, Central America and South America as well growing on bald cypress trees. The resurrection fern similarly prefers the branches of live oak trees, but will grow on rocks also taking nourishment from the air. The name, resurrection fern, was given because during a drought the leaves shrivel up and become gray, but after a rain turn green and stand up within hours, as if they came back from the dead.
A live oak tree on Jekyll Island, Georgia harbors the resurrection fern on the larger branches while Spanish moss hangs from the upper branches.
Photo by Robert M. Ungerer
I sought the reason how these plants hanging from live oak trees obtained minerals and nutrients other plants absorbed from the soil through roots. Botanists found the answer, folial leaching, a unique process found in live oak, bald cypress and other plants. The leaves and bark of live oaks shed large quantities of the nutrients, calcium, magnesium, potassium and phosphate. Rain water washes the nutrients off the leaves to trickle down from the tree canopy onto the leaves of Spanish moss and resurrection fern below. Tiny cup shaped gray scales on the thin Spanish moss leaves collect and absorb nutrient rich rain water.
The scales also trap dust particles known to contain chemicals and minerals. Fern rootlets anchored in the live oak bark absorb nutrient rich rain water. These two air plants flourish living under or on trees with high rates of folial leaching providing an environmental niche where they obtain minerals hanging in the air.
Since the live oak loses leaves periodically it appears to be alive year round and therefore forever "live." Growth is fast, reaching a diameter of 5 feet in 100 years, but dependent on sun exposure, soil quality, wind and contact with salt water spray.
The ability of Spanish moss to trap, collect and absorb minerals was utilized to measure air pollution in Sao Paolo, Brazil in 2004. Spanish moss grown in suspected pollution sites over motor vehicle roadways contained increased concentration of zinc, copper, barium, arsenic and vanadium. Increased concentrations of aluminum, iron, manganese, magnesium and lead were found in dusty sites. The results were startling for the residents who realized the multitude of metallic pollutants they breathed into their lungs. Botanists were impressed that a rootless air plant could absorb a variety of minerals.
Spanish moss has a long curly thin leaf intertwined with hundreds of leaf fragments creating a hanging mass up to 20 feet long. Insects, snakes, two species of bat, one spider species, and the parula and yellow-throated warblers may live in the hanging mass. I personally picked and probed the moss looking for insets but found none. Under magnification using binoculars reversed I observed scales and flowers on the thin leaves.
In years gone by Spanish moss was dried, washed and used for mattresses, furniture upholstery and automobile seats. Biting bed bugs have their origin from such mattresses.
The resurrection fern has a characteristic frond or leaf 5-6 inches long with leaflets attached. Reproduction is via spores released from the frond which grow on live oak bark producing eggs and sperm. Fertilization occurs when sperm swim to the eggs and then a mature plant grows.
If you visit southeastern United States, look for Spanish moss hanging from a live oak tree. Look closer, you will likely find resurrection ferns clinging to the large branches.