Red oaks can reach over 90 feet in height with trunks 3 feet in diameter.
By Steve Carroll, Contributing Columnist
Oaks are found around the world, with about 90 species in North America alone. Northern red oak (Quercus rubra) is one of the 30 or so oaks in our region and is one of our most common trees. A closely related species, southern red oak (Quercus falcata), also grows in our area, but when I mention red oak in this article, I’m referring to Quercus rubra.
Red oaks can reach 90 feet or more in height, with trunks 3 feet in diameter. In the mid-Atlantic, they are especially prominent in the mountains and Piedmont. They are frequently encountered in the inner coastal plain, but are less common along the coast. They prefer moist, acidic sites with deep, rich soil, but will also grow on exposed mountain sites with thin, rocky soil. They do well in full or partial sun, but not in deep shade.
Red oak opens its yellow-green flowers in the spring, with male and female flowers forming on the same tree. If successfully pollinated by the wind, acorns— the prototypical oak fruit— develop. Red oak acorns mature in their second season.
Acorn production varies dramatically from year to year. After several seasons with low yield, oaks across a region may collectively produce a bumper crop, a phenomenon called masting. It was long thought that this was an evolutionary adaptation to produce so many acorns that herbivores could not consume an entire year’s crop. This may indeed be a reason for this dramatic cycle, but other explanations are possible, such as increased pollination efficiency in years when many flowers form.
Red oak leaves are 4 to 10 inches long, with seven to 11 bristle-tipped lobes. Sinuses (indentations between these lobes) cut one-quarter to two-thirds of the way to the midrib. In the fall, the leaves turn orange, red or magenta.
Oak leaves are the major food source for many moth and butterfly caterpillars, and songbirds seek out and feed these caterpillars to their young. The acorns are prized by grouse, jays, turkeys, squirrels, bear, deer and other birds and mammals. However, they are too bitter for human consumption unless first leached of their tannins. It’s been said that acorns such as those from red oak are “best eaten indirectly by man, in the form of pork” (food historian Waverley Root).
In some years, oaks are heavily infested with spongy moth (formerly called gypsy moth) larvae, which can quickly defoliate a tree. One year of attack may slow growth of acorn production, but it doesn’t usually kill a mature tree.
Years ago, when my wife and I used a woodstove, we burned red oak. More recently, it was our first choice when we replaced our carpeting with hardwood flooring. Red oak is also used to make furniture, tool handles, railroad ties and other products. It has been used for barrels to hold dry goods, but the wood does not seal tightly enough to hold liquids. Native Americans and early settlers used oak-leaf compresses to heal wounds and tannin from oak bark to tan hides.
Whether as an attractive shade tree or to support wildlife, red oak is an excellent choice for landowners who have sufficient space.
Steve Carroll is a botanist and ecologist who speaks and writes about trees, gardening and the world of plants. He is the co-author of “Ecology for Gardeners,” published by Timber Press.