The Sky Islands region of southeast Arizona plays host to over 2000 species of plants. Among their ranks are trees, shrubs, succulents, vines, grasses, ferns, mosses, and herbaceous plants. Few of these species regularly grow off the ground in other plants – perched above terra firma, sometimes high above our peering eyes. When these species exhibit such proclivities, they can truly be called epiphytes – plants that grow on other plants but are not parasitic on them. While common in many tropical areas, this botanical phenomenon is exceedingly rare in our neck of the woods.
One might consider many of our vines to be epiphytes, as a majority do grow up the nearest plant. Poison ivy sometimes grows as a robust vine up various tree species, especially in riparian zones. I’ve seen it as thick as my arm, the main stem adorned with hairy-looking aerial roots.
While I shudder at my own youthful misadventures with contact dermatitis, I now admire the beauty of a poison ivy vine artfully winding its way up a tall tree. Not only does it provide additional shade to us land-bound creatures, but the fruits are highly prized by a wide range of birds as well. A number of other vines – wild cucumber, morning glories, and Gila man root among them – also are quasi-epiphytes. Their roots, however, always seem to be in the ground itself, perhaps disqualifying them as true epiphytes.
Perhaps our strangest occasional epiphytes are several species of cacti that rarely grow in trees locally. The most common species to accomplish the feat are various prickly pears. Given that their seeds are dispersed by fruit-eating mammals and birds, we no doubt have them to thank for this rather implausible arrangement. The first time I saw an aerial cactus was high atop a billboard near the
Chiricahua Mountains. While certainly not an epiphytic situation, the scene opened my mind to these familiar succulents going airborne.
Years later, I found myself in Barranca del Cobre – Mexico’s famous Copper Canyon. There I marveled at a wide range of cacti species, including prickly pears and more cylindrical species, like our hedgehog cacti, perched beautifully in a variety of trees. Large morpho butterflies and colorful birds completed the tropical scene.
Back in Arizona I soon discovered a few prickly pears growing in mesquite trees, sometimes within reach. Enough soil had apparently accumulated in the crotch of the host trees to accommodate the cacti. Still, the situation is a rare one in our parts – a mere hint of the tropics to the south. The same can be said of our fern species (particularly polypody), mosses, and lichens to a degree, as they too can be epiphytic, but most are not bound to the lifestyle. Which plant is then in Arizona?
Enter Ball Moss. Though the name is decidedly deceiving, this is a flowering plant, not a moss, whose first cousin is the more famous Spanish moss of the southeastern U.S. Both are members of the Bromeliaceae, the pineapple family. While many of our more tropical species in the Sky Islands logically trickle up from the tropics to reside in Arizona, ball moss is among the few I’m aware of that do so from the Caribbean and the deep south of the U.S.
Sometimes dubbed an “air plant”, ball moss indeed gathers much of its moisture from airborne humidity – no small accomplishment in arid Arizona! Strangely, it almost exclusively grows on red-berry (aka one-seed) juniper in our parts, though I’ve seen a few netleaf hackberries host it as well.
Sonoita Creek State Natural Area, which is nearly at my doorstep, is the best place to observe the species, including rarely on towering cliffs. Ball moss truly hits its stride, however, on junipers lurking in shady canyons. There it can grow so densely that it almost looks like a colony of ball moss hosting a juniper instead of the exact opposite!
As climate change continues to envelop us in a mega-drought, the prospects for ball moss and other moisture-loving plants is dubious at best. So, go now to see this Arizona anomaly. If you come upon its minuscule royal purple flowers or see a northern beardless tyrranulet (a tiny flycatcher) nesting in a clump of ball moss, then count yourself fortunate to have virtually traveled to the tropics. As for me, I am grateful that I live within easy walking distance of southeast Arizona’s only epiphyte.
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS LLC, their Nature Adventure & Conservation organization devoted to protecting and promoting the unique biodiversity of the Sky Islands region. RWWJ offers a wide variety of private, custom-made courses, birding & biodiversity tours. Visit: www.ravensnatureschool.org