White Oak

The following article was written by Richard Evans, UT Arboretum Director, and originally published in the Volume 21, Number 3 issue of UT Arboretum Society Journal, The Leaflet.

The National Arbor Day Foundation recently held a nationwide vote to determine America’s choice for a National Tree. People were invited to vote for one of twenty-one candidate trees, based on broad tree categories (genera) that included the state trees of all 50 states and the District of Columbia, or to write in any other tree selection. The oak was the first choice for America’s National Tree and redwood, maple, pine and dogwood rounded out the top five choices. John Rosenow, president of the Arbor Day Foundation, said, “By any standard, oak merits the distinction of being named the people’s choice of America’s National Tree.” Among the many strong attributes of oak, Rosenow cited its diversity, with more than 60 species growing in the United States. “This magnificent tree is significant in sheer number alone,” he said, “with oak trees being America’s most widespread hardwood.” “From earliest settlement of our country, oaks have been prized for their shade, beauty, and lumber, “ said The National Arbor Day Foundation news release.

“Oak’s amazing strength and longevity have also made this tree a central part of our history,” Rosenow added, “with leaders as diverse as Abraham Lincoln, William Penn, and Andrew Jackson being associated with them. Another early ‘hero’ of American history, ‘Old Ironsides,’ or the USS Constitution, was famed for repelling British cannonballs thanks to its thick, live oak hull. The American people have chosen wisely in so honoring the oak.”

In Tennessee, however, the oak yielded to the yellow-poplar (Liriodendron tulipifera) (also referred to as tulip tree and tulip-poplar) for the position of “State Tree”. The attributes of the tulip-poplar are worthy of this status, but if you were to measure its popularity as a product of its integration into the names of places, towns, creeks, parks and other such features, oaks would win the contest. One has to look no further than the environs .near the UT Arboretum for numerous examples. The most obvious is the town in which we reside, Oak Ridge, TN that derived its name from a major geological feature, Blackoak Ridge. Then there are Whiteoak Creek, Oak Valley Cemetery, Oak Lane and, not so far away a town named Oakdale and (several) Oak Grove.

With the focus on oaks it is important to note that not all of the oaks are the same. Generally we think of oaks being in two groups, white oaks and red oaks or, in technical terms, the “Leucobalanus” and “Erythrobalanus” subgenera, respectively. White oaks are recognized as having leaves without spinose (sharp-pointed) or bristle-tipped lobes; summerwood pores that are angled, small and thin-walled and; fruit (acorns) maturing in one season with the inter surface of the shell glabrous (smooth) and sweet seed. On the other hand, red oaks have leaves with bristle-tipped lobes; summerwood pores rounded, large and thick-walled and; fruit usually maturing in two seasons with the shell’s inner surface being tomemtose (hairy) and the seed usually bitter. In actuality, the assignment of a certain species to one group or the other has not been an easy task, even for the experts. No matter what feature was chosen, there were always a few species that could be put into either group because of overlapping characteristics.

Tennessee is rich in the diversity of oak species. The Tennessee Department of Environment and Conservation’s Heritage Program reports that we have 22 native oak species in Tennessee. Of these species, we have 12 species that are known to exist within in the Oak Ridge area of Anderson County, TN. These species included:

Of this group, white, chestnut, post, scarlet, southern red, northern red and black oak are common throughout Oak Ridge. However, if you are interested in finding the other more obscure species I’ll give you a few hints. Swamp chestnut, willow, Shumard and pin oak are all found in the low lying areas around streams and wet depressions. Chinkapin oak can be found on dry south facing slopes, sometimes in association with eastern red cedar (Juniperus Virginia) and as an understory tree in abandoned fields that have reverted to our native short leaf (Pinus echinata) and Virginia (P. Virginia) pines. Blackjack oak is rarely seen in our local forest, but this author has found a few individuals growing on dry infertile soils in association with chestnut and post oak. I could tell you exactly where to find these species, but that would spoil the “fun of the hunt” and the chance to test your tree identification skills.

Now this is where the real fun begins. There are some oaks that are reportedly not found in Anderson County, but curiously found in adjacent counties. For example, swamp white oak (Q. bicolor) has been located to our south in Knox County and to the north in Campbell and Scott Counties (source: UT Botany Department Herbarium; www.bio.utk.edu/botany/herbarium/vascular/atlas/dicotsd-f.html). Likewise, overcup oak (Q. lyrata), cherry bark oak (Q. pagoda, formally Q. Falcate var. pogodifolia), pin oak (Q. palustris), and dwarf chinkapin oak (Q. prinoides) are all reported in adjacent counties, but not in Anderson County. The likelihood of these species recognizing a political boundary as a limit to their range seems remote to me. More likely, we are not looking in the right place. Armed with some knowledge about the natural habitat of these trees and some tree identification skills, someone may yet experience the thrill of finding an unreported oak species. Who knows, it might be in the greenway, parks, woodlots, or your back yard. If you are really up to the challenge, you may want to see if you can add to the list of our 22 native Tennessee oaks. Just recently scientists located and verified a new unrecorded oak species, sand post oak (Q. margaretta). The hunt is on.

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