The Oaks of the genus Quercus account for more tree biomass than any other species in North America and Mexico (1). Northern Red Oak is a large native deciduous tree growing 60 to 90 feet high and up 2-1/2+ feet in diameter, with a rounded crown of stout spreading branches. The largest know Red Oak in Minnesota is in Houston County measuring 75 feet high, 66 foot crown spread, 191 inches in circumference, scoring 282 points. The U.S. National Champion in Ohio scores 456 points with a height of 92 feet, crown spread of 115 feet and a circumference of 335 inches.
The bark is brownish-gray to dark gray, smooth on young stems, becoming rough and furrowed into wide shiny flat-topped ridges that are said to resemble "ski tracks". The inner bark is reddish.
Twigs are stout, reddish-brown, smooth with large conical terminal buds that are also reddish-brown with mostly hairless scales except there may be reddish hairs at the tip of the bud.
Leaves are alternate, simple, on a slender 1 to 2 inch long smooth stalk, the blade 4 to 9 inches long and 3 to 6 inches wide, elliptical in shape, divided into 7 to 11 shallow, wavy lobes cleft 1/3 to 1/2 of the distance to the mid-vein. The lobes have bristly tips, awns, at least 12, and are rounded in the sinus. The base is obtuse to truncate. The upper surface is a dull green, the underside a dull lighter green with tufts of hair along the mid-vein. As with most oaks, leaf shapes can be quite variable. Fall color is an orangish to reddish-brown usually turning glossy maroon to brown.
Flowers: The tree is monoecious, that is with separate male and female flowers. Male flowers are a yellow-green, appearing in slender catkins, 2 to 4 inches long at the ends of the prior years growth. Each male flower has six stamens (can very from 2 to 12), which have long spreading white filaments when the flower fully opens. The female flowers are more reddish-green and appear as small slender spikes in the axils of new growth. They have 3 (to 6) carpels and styles that are slender and short. There are no petals; both sexes have the sepals are fused together. Both appear with the leaves.
Fruit: The female flowers mature to an egg-shaped acorn, 5/8 to 1-1/8 inches long, about 1/4 enclosed in a broad reddish-brown cup-shaped cap (this is highly variable as to cap coverage and acorn size by geographic location) with blunt tightly overlapping scales that often have dark margins. The scales at the cap margin do not turn inward. The cap is said to resemble a 'beret'. The acorn matures in the second summer as do most species in the Quercus Sect. Lobatae - the Red Oak Group. They appear in groups of 1 to 5 on a short stalk. The nut is light brown to grayish and can germinate immediately on falling from the tree. Dispersion is by animals. Trees require considerable age before bearing - upwards of 25 years.
Habitat: Northern Red Oak grows from a deep taproot and spreading lateral roots. It will re-sprout from a cut stump. Its preferred habitat is a rich moist but well drained soil such as an open wood or open area. It accepts a variety of soil types and is moderately shade tolerant. Full sun is required for good growth. This is our most rapidly growing Oak species. Red Oak will hybridize with Pin Oak, Northern Pin Oak and Black Oak. It is also susceptible to Oak Wilt, which has decimated large stands of Red Oak in the metro area and in the Garden. Oaks should be pruned during the winter months, from October to March, to avoid open wounds where the Oak Wilt fungus can enter.
Names: The genus name, Quercus, is the Latin word for Oak. The species, rubra, means red and refers to the color of the inner bark. The author name for the plant classification from 1753, 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Above: Oak leaves can be quite variable. Red Oak leaves are elliptical in shape, divided into 7 to 11 shallow, wavy lobes cleft 1/3 to 1/2 of the distance to the mid-vein. The lobes have bristly tips and are rounded in the sinus of the lobe. The upper surface is a duller green.
Below: 1st photo - The underside has some tufts of hair along the mid-vein. 2nd & 3rd photos - Red oaks have a stout trunk and a broad rounded crown. Two examples.
Twigs are stout, reddish-brown, smooth with large conical terminal buds that are also reddish-brown. 2nd & 3rd photos - Bark is brownish-gray to dark gray, smooth on young stems, becoming rough and furrowed into wide shiny flat-topped ridges that are said to resemble "ski tracks".
Below: 1st photo - Female flowers arise in the leaf axils of new growth. 2nd photo - The male flower catkins as they are forming and 3rd photo - fully extended to release pollen.
Above and below - Acorns: The acorn is egg-shaped, about 1/4 enclosed in a broad reddish-brown cup-shaped cap which has blunt tightly overlapping scales that often have dark margins. The cap is said to resemble a 'beret'. The examples below show how much or how little of the acorn the cap can cover.
Below: Fall color is an orangish to reddish-brown usually turning glossy maroon to brown.
(1) Ascent of the Oaks, Hipp, Manos, Cavender-Bares, SA, Aug 2020.
Northern Red Oak is indigenous to the Garden. Eloise Butler catalogued it on April 29, 1907. Like the White Oak, in North America it is found in the eastern half of the continent, from Minnesota to Louisiana and eastward to the coast, excepting Florida. In Canada it is known in Ontario, Quebec and P E Island. Within Minnesota it has a larger range than the White Oak. It is generally found north and east of a diagonal line drawn from Freeborn County in the south to Polk in the NW, with some scattered exceptions.
There are six species of Oak generally found in parts of Minnesota that are not considered hybrids or rarities that have not been collected in the last 100 years. These are: White Oak, Q. alba; Swamp White Oak, Q. bicolor; Northern Pin Oak, Q. ellipsoidalis; Bur Oak, Q. macrocarpa; Northern Red Oak, Q. rubra. and Black Oak, Q. velutina. Chinkapin Oak (Chestnut Oak, or Yellow Oak), Q. muhlenbergii was native but is historical only now, last collected in 1899; Scarlet Oak, Quercus coccinea, can also grow here as can Pin Oak, Quercus palustris, but neither are native.
Uses: Northern Red Oak is the most important source of Oak hardwood lumber, used for flooring, cabinetry, furniture, millwork and many rougher uses and except for certain specialized uses such as liquor barrels, it has replaced White Oak due to its rapid growth characteristics. It is heavy, hard, strong, coarse-grained and machines well. The acorns are edible although bitter and with more tannin than the White Oak group. Bitterness is removed by leaching and the tannin by boiling. Native Americans made use of most acorns for acorn-flour. Fernald (Ref. #6) has some detail on how this was done.
It is difficult visually to separate the species of the Red Oak group when you are looking a piece of lumber. As a general characteristic the Red Oak group has wood with the tallest rays less than 1 inch and the latewood pores are few and distinct. Whereas, in the White Oaks the tallest of the largest rays are greater than 1-1/4 inches and the latewood has numerous small pores that grade into invisibility. A small hand lens is necessary to do this. In terms of hardness, Red Oak is 1280 on the Janka Wood Hardness Scale. White Oak is 1320 and Hickory, North America's hardest wood, is 1820. World-wide, Lignum vitae is the hardest at 4500.
Francois Michaux writes in North American Sylva of 1817-19 (Ref. # 26b): "The wood is reddish and coarse-grained, and the pores are often large enough for the passage of a hair; it is strong but not durable, and is the last among the Oaks to be employed in building. Its principal use of for staves, which, at home [France], are used to contain salted provisions, flour, and such dry wares as are exported to the islands, and in the colonies, to receive melasses and sugar.
The bark consists of a very thin epidermis and a very thick cellular tissue. It is extensively used in tanning, but is less esteemed than that of the Spanish, Black and Rock Chesnut Oaks.
The Red Oak was one of the earliest American trees introduced into Europe. Large stocks are found on the estate of Duhamel, which yield seed abundantly, and even multiply naturally; but the quality of its wood is so inferior, that I cannot recommend its propagation in our forests."
Conditions have obviously changed since 1819. Red Oak is extensively used to today for interior wood work and furniture which only highlights the loss in our forests of those other species which were more highly esteemed in Michaux's day.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"