Few sights are more evocative of the Lowcountry than a live oak tree draped with beardlike garlands of Spanish moss (Tillandsia usneoides).
Over the past decade or so, a more compact relative of Spanish moss has also been found growing on tree branches in coastal South Carolina. It’s called ball moss (Tillandsia recurvata) because of its distinctive, spheroid growth form and scaly, grayish-green leaves.
Ball moss is native to Mexico, the Caribbean, Central and South America, plus portions of the southern United States.
Common in Florida, it seems to have spread to coastal South Carolina as a hitchhiker on nursery plants. Look for its rounded, spiky balls on young live oaks, crepe myrtles, magnolias, and shade trees in parking lots and other newly planted suburban environments.
Like Spanish moss, ball moss isn’t a true moss at all. Both species belong to the bromeliad family, a mainly tropical group that includes some 3,475 other kinds of flowering plants, including pineapples.
Also like Spanish moss, ball moss isn’t a parasite and doesn’t damage its host. Instead, it’s an epiphyte (“air plant”), using trees merely for support, as it doesn’t need soil in which to grow. Masses of plants may even colonize power lines or other inert substrates.
Aerial habitats provide access to more light and less competition, perhaps, from other species.
Like other green plants, ball moss manufactures its own food by photosynthesis, absorbing water and nutrients from rainwater, the atmosphere, and debris.
In the fall it produces small, pale violet flowers on thin stalks; these give rise to brown capsules packed with tiny, dry seeds that are spread by the wind. Thin projections on the seeds help wedge them into bark or other rough surfaces.
Ball moss is surprisingly resistant to desiccation. Although lacking traditional roots, it’s covered by numerous tiny, leaf hairs called trichomes, which absorb water like minuscule sponges.
Also, when water is scarce, ball moss keeps its stomates (leaf pores) shut during the daytime, reducing water loss in the hot sun. At night, the stomates open up, collecting carbon dioxide gas — one of the basic ingredients needed for photosynthesis.
Overnight, ball moss stores carbon dioxide by converting it into an organic compound called malic acid. During daytime, the malic acid is broken down to release the captured carbon dioxide, which is then available for photosynthesis.
Ball moss is one of some 16,000 drought-resistant plants, including cacti and many succulents, that show this interesting adaptation.
This unassuming little air plant may also have a promising future in “green architecture” — eco-friendly construction practices designed to safeguard human health and the environment. Recent research suggests that ball moss planted en masse on rooftops could help lower air temperatures, reduce runoff, and provide habitats for urban wildlife.