The chestnut oak, Quercus prinus, is also known as rock chestnut oak, mountain chestnut oak and rock oak. I recently noticed this impressively large and beautiful tree at Clinton Nature Preserve near Villa Rica, Georgia where I took my grandson to a high school cross-country meet. Chestnut oak trees lined the entrance to the park, and fit very well in the landscaping of the large area. The tree’s niche in the natural is to grow on ridges and in rocky, dry and infertile soil that other trees find difficult. The chestnut oak has interesting strategies for survival, and has had many important uses.
Native to the Appalachian area extending from Canada to northern Georgia, Alabama, and 
Mississippi, the chestnut oak has difficulty surviving as an understory. The tree is often overshadowed by faster growing trees. To illustrate how shade influences the tree, seedlings from acorns in one uncut forest grew only 6 inches in 10 years, and most died in only a few years. However, seedlings in clear-cut areas with plenty of light grew to over 6 feet and sprouts from stumps grew to 21 feet in the same amount of time. In times of fire, dry weather or diseases, the tree is poised to quickly regain dominance. Likelihood of dominance is also increased by its adaptation to grow in dry, rocky areas in which other trees falter. To help protect itself from attack by diseases and insects such as the gypsy moth, the chestnut oak produces a high level of tannin in its bark, twigs, leaves and roots. This tree has effective strategies for survival in a difficult environment.
Tannin has proven to be useful to people as it is to the chestnut oak. I am reminded of a sign near Union Springs, Alabama that reads ‘Tanyard’, but nothing is there. Once a farming community with a tanning operation, the area now appears deserted. Before the 1900’s, tanyards such as this one were frequent, and depended primarily on oak trees to supply tannin for the tanning process. The bark, roots, twigs and branches of local trees were stripped and dried, primarily in the spring when tannin levels were highest. They were then coarsely ground in a grist mill powered by streams or creeks. Soaking this mulch for several days released water-soluble tannins into the water. As this was going on, 
hides and skins were dipped in vats of water and lime, or water and hardwood ashes, to loosen hair and tissue. The hides and skins were scraped and rinsed repeatedly, with a mildly acidic final rinse added at the end, to de-lime and remove hair and tissue. Dipping these hides and skins in vats of increasing concentrations of tannin water could preserve them, but this process required as many as three years to produce good leather. The preferred method was rotating the hides and skins in a large drum, using water power, so that the hides and skins could be brought in rapid and repeated contact with tanning solution. This sped the process to only three months. After cleansing the leather of tannin, it was oiled to prevent drying and cracking. Leather from this process was made into shoes, belts, saddles, suitcases, and other items requiring stiffer leather. There is an interesting web video from Hermann Oak Leather Co. illustrating this process. Faster and cheaper non-organic methods of tanning has largely replaced the 
use of tannin, but oak-tanned leather is still considered highest quality.
Other uses for tannin are in dyes, as a developer in photography, and in clarifying wine and beer. Tannin is used in the production of an anti-corrosive primer for treatment of rusted steel surfaces prior to painting. Tannins serve many useful purposes, and oak trees including the chestnut oak are important sources of this chemical.
Chestnut oak is a member of the white oak group. Trees usually grow to a height of 60 to 70 feet, and occasionally to 100 feet. Trunk diameter is 3 to 4 feet, and rarely to 6 to 7 feet. The trunk divides at 15 to 20 feet above ground into large spreading limbs 
that form a wide, spreading crown. Bark on the tree is ¾ to 1½ inches thick, and it is heavily fissured with deep and wide v-shaped valleys. Color of bark is silver-gray to redish-brown, ultimately turning dark gray or brown. Buds are ¼ to ½ inches long and ovate, with bright chestnut-brown scales on their margins. Leaf edges are wavy, in a coarsely notched, uniform pattern. Leaves are 5 to 9 inches long and 1½ to 3 inches wide, alternate, simple and oblong. The leaf is shiny and yellow-green on the upper surface and lighter and slightly fuzzy underneath.
Male and female flowers are on the same tree, and develop along with the leaves. Male flowers are long catkins that develop from terminal buds of the previous year’s shoots. Development begins when minimum air temperature remains above 50 degrees F for more than 10 days. Female flowers develop on short green stalks from the axils of new leaves, about a week after the male flowers. They have a yellow calyx, with dark red stigmas. Fruit is an egg-shaped acorn, pointed at the apex. It is shiny 
and lustrous chestnut brown. The acorn is 1 to 1½ inches long and 5/8 to 1 inches thick. About 1/3 to 1/2 of the length is enclosed in a turbinate pericarp that is unique in that it retains moisture to help germination in dry weather. The kernel tastes bitter due to tannin, but less so than many other oaks. Chestnut oak acorns mature in one season and drop in early September to early October. Production of acorns is erratic from year to year, and germination of them occurs in the fall.
Much has been said about white oak and chestnut oak acorns being less bitter and more palatable than other acorns. The appearance is that there is less tannin in these acorns, but this is not true. The fact is, if these acorns are ground making the tannins more available before tasting, they would taste very bitter. All acorns are edible, if tannins are removed. There is much information and many recipes related to this on the internet, if interested.
The chestnut oak is an easily identified tree. Its timber is valuable, and sold as a white oak. The tannin abundant in its bark, twigs, and roots has incredible uses. The tree is an impressive shade tree, great for large landscapes. The acorns can be eaten with proper preparation. It is interesting how many important uses have been found for this tree.
The book featured below on tanning is good reading for anyone interested in the process. It is available here in Kindle, paperback and hardback, through my participation in the Amazon Services LLC Associates Program. Any purchase through this link helps maintain this website and is appreciated.
