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Wednesday, 22 May 2013 00:00

Plants hitch a ride to the sun

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backthenA book I read about the Suwannee River featured numerous photographs of trees overhanging the waterway festooned with Spanish moss. Spanish moss isn’t, by the way, a true moss at all but a vascular plant that reproduces via tiny flowers. But it is an epiphytic plant; that is, a plant which grows upon another plant or object for support. 

 

All of the Spanish moss in the book’s photos set me to thinking about epiphytes and the fact that we have a modest array of them here in Western North Carolina. Most of our lichens, for instance, are epiphytic upon rocks or trees.  

The most conspicuous lichen perhaps is old man’s beard (also misnamed “Usnea moss”), which dangles from the branches of trees in miniature gray-green Spanish moss-like banners. Numerous bird species — especially ruby-throated hummingbirds, blue-gray gnatcatchers, and northern parula warblers — use the plant to line, waterproof, camouflage and decorate their nests.

The true mosses found here that are epiphytic on logs, rocks, trees, roofs, etc. are legion. One of the most common and easily distinguished is called “fern moss” as it closely resembles a tiny fern.  

Ferns are the showiest and most dramatic “air plants” encountered in WNC. The most interesting, for me, is walking fern, which appears on rocks or walls (especially limestone) and has the capacity to root from the tips of its leaves so that, through time, the plant literally traverses or “walks” across its stony domain. 

But resurrection fern comes closest to epitomizing the showy, luxuriant, way-up-in-the-air growth forms we tend to think of when the terms epiphyte, air plant, passenger plant or perching plan are utilized. It does, after all, flourish in the true tropics where perching orchids, bromeliads and other exotic flora find their homes in the tops of trees.

In WNC, resurrection fern is fairly common, growing on moss-covered rocks and old shingled roofs, as well as upon the trunks and outstretched branches of oaks, elms and other tree species. It has the peculiar habit of curling up into a ball when dry so as to conserve energy. They are then revived and unfurl at once during rainy periods. I’ve observed it through binoculars as high as 50 feet or so above the ground.  

One of my favorite natural history books is Plantwatching: How Plants Live, Feel, and Work (London: McMillan, 1988) by Malcolm Wilkins, a botanist at Glasgow University. Therein, Wilkins presented a clear account of just why some plants are epiphytes and how they manage to pull it off so far above the mineral-giving soil.

“Epiphytes, then, do little more than ‘hitch a ride’ on the host plant, and their principal gain is simply a more favorable position, higher in the sun-lit layers of the canopy,” he observed. “The main problem for epiphytic plants is to obtain an adequate supply of mineral nutrients, and these appear to be collected from trickling rain water, the ion content of which is no doubt enriched by the leakage of ions from the dead and dying cells of the host tree’s bark.”

Maintaining a place in the sun has always been tricky business.

George Ellison wrote the biographical introductions for the reissues of two Appalachian classics: Horace Kephart’s Our Southern Highlanders and James Mooney’s History, Myths, and Sacred Formulas of the Cherokees. In June 2005, a selection of his Back Then columns was published by The History Press in Charleston as Mountain Passages: Natural and Cultural History of Western North Carolina and the Great Smoky Mountains. Readers can contact him at P.O. Box 1262, Bryson City, N.C., 28713, or at This email address is being protected from spambots. You need JavaScript enabled to view it. .      

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