Tree of the Month, October 2023

Northern Red Oak, Red Oak

Quercus rubra

(Q. Borealis in many older texts)

by Martin (Mort) Schmidt

for Simply Living

Mature Northern Red Oak. Photo by Mort Schmidt. 

Northern Red Oak is one of the Midwest’s most important trees. Oaks are host to numerous animals, provide food for rodents, bears, deer, and other animals, and are essential sources of wood. Quercus rubra and Pin Oak (Q. palustris), are the most abundant of the red oak group in Central Ohio. Oaks are found over much of the world, but red oaks are native to North America, which is why we have the greatest variety of oaks. 

Notice that the term “Red Oak” can mean the species Quercus rubra, but also other species in the red oak group. (The same is true of “White Oak”, which can mean the species White Oak (Quercus alba), but also other species in the white oak group). Here I’ll use “Northern Red Oak” for the species, and “red oak” for the group (also called the “black oak group”, just to complicate things). There are differences between the leaves, buds, bark, and wood of red oaks and white oaks, but the criitical difference is that white oak acorns sprout soon after falling, while red oak acorns sprout the following spring. 

Northern Red Oak leaves are simple, meaning that they’re attached directly to twigs and branches with their own individual stems, whereas compound leaves consist of 3, 5, 7, or more leaflets, depending on the species, attached to a shared stem. Also, Northern Red Oaks are alternately arranged. Oppositely-arranged leaves (and branches) are directly across from each other, while alternately-arranged leaves are staggered.

Top and bottom left – Alternate branching. Top and bottom right – Opposite branching. Drawing and photo by Mort Schmidt.

Northern Red Oak leaves have a familiar shape. They’re pinnately veined, with a primary vein along its length, as opposed to palmately veined, with multiple veins radiating from the base. Like most oak leaves, Northern Red Oak leaves have distinct lobes, and like most members of the red oak group, they have pointed tips. Northern Red Oak leaves are typically fatter than Pin Oak, and narrower than Black Oak (Quercus Velutina). But there’s a lot of overlap between species, so other features help to distinguish them. Little matter – they’re all red oak at the lumber yard. Furthermore, oaks often hybridize, so a tree might belong to more than one species. 

Pinnate versus palmate veining. Drawing by Mort Schmidt.
Left to right – Pin Oak, Northern Red Oak, and Black Oak. Photos by Mort Schmidt.

Northern Red Oaks have a height of around 80 feet at maturity, with a trunk diameter of 2 to 3 feet. Ohio’s Champion, located in Ashtabula County, has a height of 92 feet and a trunk diameter of 8 feet, according to the Champion Trees of Ohio website.   

Northern Red Oak has the largest red oak acorns in Ohio. At maturity they’re an inch or more long, and their caps are shallow, resembling Frisbees. Pin Oak leaves can be similar, but their acorns are half the size of Q rubra. Pin Oaks are also distinguishable by their drooping lower branches and their presence in wet soils. Black Oaks leaves are also similar to Northern Red Oak, but their acorns are smaller and their caps are much deeper. Black Oak bark is also yellow or orange beneath the surface. 

Left to right – Acorns of Northern Red Oak, Pin Oak, and Black Oak. Northern Red Oak has the largest acorns with the shallowest caps. Photos by Mort Schmidt. 

Oak flowers consist of catkins, and the differences between species aren’t obvious, at least not to me. They look nothing like the flowers you’d put in a vase, but they make pollen, receive pollen, and make fruits, which qualifies them as flowers. Oak flowers are wind-pollinated, and because they don’t need to attract insects, they lack the appearance we associate with flowers. Northern Red Oaks are monoecious, i.e., they have male and female flowers on the same tree. Northern Red Oak bark, like Pin Oak bark, is dark gray and is distinguished by its long, smooth ridges. A useful trait for recognizing both red and white oaks in winter is their multiple terminal buds. Like leaf tips, white oak buds are generally rounded, and red oak buds are pointed, but the difference can be subtle. 

Clockwise from upper left – Northern Red Oak flowers, bark, and buds. Photos by Mort Schmidt. 

Quercus rubra prefers moist but well drained soil, and because it tolerates urban conditions and has few objectionable traits, it’s a popular street tree. The other common red oak in Central Ohio, Pin Oak, inhabits wetter soils, but there is a fair amount of overlap in their habitats. 

Range of Northern Red Oak. Image from US Geological Survey

Northern Red Oak is the most widespread, and commercially, the most important red oak. It’s also relatively fast growing, and can provide lumber in the life of the person who planted it. Q. rubra lumber has a Janka hardness of 1,220 lbf and a density of 0.70 g/cc, according to the Wood Database, compared to the median of my list of 68 Ohio trees of 1,010 lbf and a 0.61 g/cc. Unlike members of the white oak group, red oaks are not especially rot-resistant. White oak pores are filled with foam-like tyloses that block the flow of liquids, while red oak pores are open to moisture and fungi, which promote decay. 

Ash, oak, and hickory are Ohio’s main ring-porous woods. These woods have distinctly larger pores aligned with the annual rings, which make them split readily along its length. Before the invention of power saws, woodworkers found it easier to split boards along the grain than to saw them, so oak lent itself to use as barrel staves, fence posts and rails, etc. However, the lack of tyloses in red oak made it suitable for slack cooperage (barrels for dry substances), but not tight cooperage (barrels for liquids). That’s why wine and whiskey are stored in white oak barrels. 

Oak showing its characteristic ring-porosity. Photo by Mort Schmidt. 

Northern Red Oak was, and is widely used for furniture, flooring, railroad ties, and countless other things. But because of its relatively coarse grain, maple or beech are better for cutting boards, rolling pins, and other kitchen ware, because they are smoother and have less tendency to hold flavors. Northern Red Oak bark was also the primary source of tannic acid used for tanning leather, according to William B. Werthner’s “Some American Trees“. And oak makes great firewood, because of its high fuel value and ease in splitting. 

Red oak acorns have more tannins than white oak acorns. Consequently, they’re less sweet and can wait until spring to send down roots, with less risk of being eaten. They also thwart animals by producing bumper crops of acorns some years  – “mast years” – and few or none in other years. Animal populations are limited by the amount of available food in lean years. Then in mast years, there are more acorns than the animals can eat, and acorns have a better chance of becoming trees. Squirrels and other rodents eat acorns, including red oak acorns, as do deer, bears, and other animals. The Indians ate acorns too, but they preferred white oak acorns when available, and ate them after extended soaking, boiling, or burial to remove the tannins. According to Rebecca Rupp’s Red Oaks & Black Birches, The Science and Lore of Trees, oak trees provide around 5,000 acorns in a mast year, so mature Northern Red Oaks can provide a lot of food.

According to the Native American Ethnobotany Database, many Indians consumed Quercus rubra acorns, including the Ojibwa, Omaha, Pawnee, Ponca, and Potawatomi. A number of them reduced the acidity by soaking them in lye, especially lye made from basswood ashes (aka Tilia, or “Linden”). Many other Natives used Northern Red Oak bark, leaves, or roots to make medicine, including:

  • Antidiarrheal – Cherokee, Dakota, Malecite, Micmac, Ojibwa, Potawatomi 
  • Throat and respiratory – Alabama, Cherokee, Delaware, Ojibwa
  • Dermatological problems – Alabama, Cherokee, Iroquois. 

Ancient texts, including the Bible, often used the word “oak” to describe trees of various types, especially sacred or culturally significant trees (but since Q. rubra is a New World species, early writing was not about this particular tree). Oaks are said to attract lightning – “Beware of an Oak, it draws the stroke”. This might be why Thor, the Norse god of lightning and thunder, was associated with oak. And finally, Northern Red Oak is the State Tree of New Jersey. 

The only objectionable “oaks” are Poison Oak (Toxicodendron pubescens and Toxicodendron diversilobum), which aren’t oaks at all, but members of the sumac family. It’s no wonder that oaks are among our most revered trees, as they provide us with food, shelter, medicine, and fuel.


You can also listen to my talks on Ohio Broadleaf Tree Identification on YouTube, Part 1 and Part 2

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