Few sights are more evocative of the South than a spreading live oak tree festooned with Spanish moss -- "hanging down from the limbs like long gray beards," as Mark Twain wrote in Huckleberry Finn.
Despite its common name, Spanish moss (Tillandsia usneoides) isn't a moss at all, but a flowering plant in the pineapple family.
And contrary to popular belief, Spanish moss isn't a parasite. Dense garlands of this grayish-green plant cause little to no damage to a tree, aside from occasionally weighing down older branches during wet weather and causing them to break and fall.
An epiphyte ("air plant"), Spanish moss uses tree branches for support. Its wiry, branching, rootless stems--up to 15-20 feet long--bear tiny leaves with numerous overlapping scales. The scales open outward when it rains, allowing the plant to soak up moisture. During droughts, the scales retract.
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Spanish moss makes its own food via photosynthesis and absorbs calcium, potassium, phosphorus, and other minerals leached out in rainwater from the tree's leaves.
In late spring, the plant produces nondescript yellowish-green flowers, followed by capsules that release tiny wind-dispersed seeds.
Spanish moss sometimes grows on bald cypress, sweet gum, and a few other trees, but in the Lowcountry it clearly favors live oaks. The deep cracks and furrows of oak bark provide places for seeds or displaced stem fragments to lodge and grow.
Spanish moss is eaten by deer and wild turkey, and it's used as nesting material by egrets, mockingbirds, warblers, owls, and squirrels. It shelters a host of other animals, from spiders and insects to snakes, anoles, tree frogs, and bats.
Although chiggers are widely assumed to be abundant in Spanish moss, especially in clumps that have fallen to the ground, several scientific studies suggest they're not common inhabitants.
Spanish moss has been the subject of colorful stories and legends, giving rise to the "Spanish" part of its common name -- perhaps a reference to the long beards of early Spanish explorers.
Native Americans and early colonists used the plant for kindling and as caulking material for houses.
Later, during the mid-nineteenth and early twentieth centuries, commercial mills in Louisiana and Florida harvested Spanish moss for use as high-quality stuffing in mattresses and car seats. A single large oak tree might yield a ton of Spanish moss along with associated debris. The curing process took several months and involved stripping off the outer greenish covering of the stem to reveal a black, horsehair-like core in the center.
Synthetic fibers ultimately replaced Spanish moss in the upholstery industry, but the plant is still used today by florists as packing material and mulch.
Vicky McMillan, a retired biologist formerly at Colgate University, lives on Hilton Head Island.