The Secret Life of Spanish Moss

Spanish Moss

Tillandsia usneoides

Bromeliaceae

A fond childhood memory originated when my Lake Alfred grandmother sent a box of Spanish Moss to my home in West Virginia.  Perhaps the Spanish Moss was packing material for something else.  If so, the something else is long gone, and the moss memory lingers.  Amazing exotic stuff for West Virginia kids!  It still amazes me.  All my life I’ve believed the name “Spanish” Moss refers to the beards of the Conquistadors.  Hope that’s correcto.  One thing is sure:  it is not a moss.

Spanish Moss flower (by JB)

Spanish Moss is Tillandsia usneoides, a Bromeliad.  Native plant enthusiasts know that most epiphytic Florida Bromeliads, “airplants” to some, are species of Tillandsia.  Arguably the prettiest is Cardinal Airplant (Tillandsia fasciculata).  Gardeners know a different array of Tillandsias and a much broader family of Bromeliads, from Pitcairnias to Pineapples.

Walking across the PBSC campus this morning, I ducked a tree-beard and noticed it to be in full bloom.  It wants attention, so here we go.

This plant hangs around unrooted, not even enjoying  the obvious tree-top adaptations of other epiphytes, such as the tanks of bigger Bromeliads, the pseudobulbs and specialized roots of Orchids, or the hairy rhizomes of Polypody ferns.  How does Spanish Moss get away with it?   How does it take in water?  How does it photosynthesize up there in the sun without frying?   Does it have a sex life?

On the sex life.   Spanish Moss relocates vegetatively as fragments blow in the wind or cling to birds.   Beyond such cloning there are pretty little greenish flowers, which when pollinated make little capsular fruits releasing tiny little wind-borne fluffy seeds.  Just a guess here, but I’ll bet when those seeds parasail from one tree to another they often  catch in pre-existing Spanish Moss, giving them a soft landing (and a future sex partner).

The water issues.  Spanish Moss and other Tillandsia species get their gray grainy look from a covering of hyper-absorbent scales that trap water and dissolved nutrients from rain, mist, dew, humidity, and bug spit.  You could scarcely design better water-catcher-holders if you tried.  The bases of the scales penetrate the leaf surface and conduct water downward into the plant like reverse roots.  The entire mechanism is refined and effective.  When dry, the winged edges of the mushroom-shaped scales tilt upward, admitting water underneath.  When that occurs, the edges come down, capturing the water and allowing it to absorb into the dead hollow scale cells.  The water passes from the wings to the center of the scale.  The cells at the very center have thick upper walls, which lift when the cells are filled with water.  As the water empties downward through the base of the scale into the leaf the thick upper walls of the central cells pull downward sealing the water in.  Think of water swirling down a drain pulling the drain plug closed.

Leaf scale from Spanish Moss. Top scale is dry. Bottom scale is wet, showing passage of water into the plant. Credit is given in article.

But why doesn’t that skinny little stem dry out in the Florida sun?  In addition to the scaly covering, Spanish Moss has a special ability found   scattered throughout desert plants.  Let’s define the problem:  a plant needs to breathe in carbon dioxide just as we breathe in oxygen.  But, just like us, the cost of “breathing” is water loss.  When the sun is hot and harsh the cost (water loss) can exceed the benefit (breath of life) when the two happen simultaneously, as in people, dogs, and most plants.  But Spanish moss and desert plants have what’s known as CAM photosynthesis.  This is not the place to ponder the anatomical-biochemical mechanisms, but rather to comment superficially that Spanish Moss and other CAM plants breathe in their carbon dioxide during the cool moist night, then store the carbon dioxide for use in photosynthesis during the dry sunny day.

The “usneoides” in the name refer to a lichen, Usnea, which looks and behaves in much the same way despite being unrelated as can be; a lichen is a combination of a fungus and alga.  Lichens have two famous abilities:

1. They can dry out and go into “suspended animation” until rehydrated.  So can Resurrection Ferns, Selaginellas, and Spanish Mosses.

2. They capture radiation and air pollution.  So does Spanish Moss, which is especially prone to capture toxic heavy metals form the foul air.  Pollution accumulation has been suggested as a reason Spanish Moss is rare within New Orleans but abundant in surrounding areas.

                                         Spanish Moss has many uses (Photo stolen from Internet)

Anything as absorbent, plentiful, and soft as Spanish Moss can be assumed to have historical uses.  Those for Spanish moss abound, florists’ wrappings, insulation, bird’s nests, and the one use that just has to be mentioned is flaming arrows.

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Confessions:  I’m using the same essay for both my blogs this week—they overlap.   The drawing of the leaf-scale comes from Benzing, D. H. Vascular Epiphytes: General Biology and Related Biota. P. 105. 2008.