Do you have favorite trees? I do. Here on the North Carolina side of the Great Smoky Mountains National Park, where I’ve resided since 1973, there are perhaps 120 species. I wouldn’t want to do without any of them. But there are some that I look for year in and year out.

In no particular order, here’s my current top 10: Fraser, cucumber, and umbrella-leaf magnolia (no bigleaf magnolia has ever been reported from the Blue Ridge province of North Carolina, although it does occur in the Piedmont region); basswood; table mountain pine; mountain ash; butternut walnut; rosebay rhododendron (the only one of the Blue Ridge’s three evergreen rhododendron species that attains arboreal proportions); chestnut oak; and yellow birch.

This time next year I would probably come up with a different list; however, yellow birch (Betula alleghaniensis) will likely be on my list every year for the rest of my life.

On north slopes and in cool ravines or watersheds, yellow birch will appear in the lower elevations of the southern mountains. But it is most common above 3,500 feet. It is one of my primary indicator species for northern hardwood forests.

Yellow birch can sometimes be tricky to identify. Trees less than two feet in circumference are easy. These display bark that is shiny (yellow or silvery) in color. The bark peels off in distinctive papery, horizontal curls that lend the tree a shaggy appearance. Older, larger, taller trees, however, change appearance. The bark loses the telltale horizontal patterning associated with birch species, becoming rough with plate-like scales. If it’s winter or the leaves are too high to examine, you can ponder awhile before making an accurate identification. (The “yellow” designation in the common name is perhaps applied more in reference to the rich golden fall foliage than to bark color.)

Older trees will sometimes stand until they are little more than sheaths of bark filled with dry punk wood. Native Americans collected this material and used it as fire tender. Yellow birch is perhaps the most important lumber species in its genus. Today, its close-grained wood (dark-brown to reddish-brown) is used for interior finishes, veneers, tool handles, snowshoe frames, and sledges. Formerly, it was used for the underwater parts of vessels, ox yokes, bunkhouse logs, and hubs that would hold wagon wheel spokes more tenaciously than any other wood.

In The Trees in My Forest (NY: Cliff Street Books, 1997), biologist Bernd Heinrich observes that in New England ruby-throated hummingbirds feed at the “sap wells” yellow-bellied sapsuckers drill in yellow and other birch species. Not able to locate the reddish or orangish flowers (cardinal flower, trumpet vine, jewelweed, etc.) hummers normally feed upon farther south, the birds not only chow down on birch sap but they also feed upon the insects attracted to the wells.

I’m particularly fascinated by yellow birch because of its tactic of colonizing various sites in a peculiar manner. Numerous observers have noted the propensity of yellow birch to germinate upon stumps or fallen logs called “nurse” or “mother” logs. A description of this tactic is provided by Rose Houck in A Natural History Guide — Great Smoky Mountains National Park (Boston: Houghton Mifflin, 1993): “Birches often appear to stand on stilts. The prop roots begin to grow when a birch seed falls onto a rotting, moss-covered log. The seed germinates, and as the seedling grows the roots are anchored to the ‘nurse log.’ Eventually the nurse log decays and disappears, leaving the birch supported on roots that reach out like the arms of an octopus.”

Sometimes these stilts will merge, thereby extending the trunk down to ground level; sometimes, they remain for years as stilts. Houck continues with thoughtful insight regarding this germination-growth strategy: “This interesting habit is almost epiphytic. Epiphytes are most common in trees in the tropics, where they can survive because of the high humidity and special adaptations that allow them to remove and store water and nutrients from the air. The incredible moisture of the high elevations in the Smokies lets these young birches survive up off the ground. Elsewhere such a habit would lead to excessive water loss, and the tree could not live.”

Yellow birch seeds also have the capacity to germinate in moss mats that cover large boulders. The ancient high-elevation periglacial boulderfields found south of Pennsylvania in the Appalachians are sometimes entirely colonized by yellow birch. Whether on isolated boulders or in extensive boulderfields, the “guest tree” literally seals itself to its “host” as the downward-descending stilt roots wrap around the rock and become firmly rooted in the ground.

One of the most striking instances of this relationship (let’s call it “the yellow birch-boulder syndrome”) is located in Horse Cove several miles east of Highlands. Near a 400-year-old tulip poplar locally known as the “Big Poplar” or “Bob Padgett Poplar,” is a very large and old yellow birch that displays scaly bark plates. It’s perched high upon a large boulder, leaning precariously toward the spot in the ancient canopy where it originally found light. Some of the stilt roots appear to have penetrated the host rock. I am fairly confident that, if the tree falls, it won’t topple off the boulder; rather, I’m betting that its tight embrace will upturn the boulder.

In the nooks and crannies of the yellow birch root system that crisscross the boulder, seeds of other species-including rosebay rhododendron, eastern hemlock, and tulip poplar-have found adequate soil deposits, germinated, and flourished. Rock host and arboreal guests reside there in a harmonious, intertwined relationship initiated perhaps 250 or more years ago.

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 ellisongeorge@cs.com.