Knowing Our Oaks

Jul 10, 2018

In this month's installment of Field Notes Scott Bowe of Kemp Station discusses Wisconsin’s oaks and how they are used in our daily lives.

Oak trees are the most abundant trees in Wisconsin next to our maples.  Oaks fall into the genus, Quercus, and are members of the Beech Family, Fagaceae. Oak is found across the United States and across the world in the Americas, Europe, Asia, and North Africa – absent only in Australia and Antarctica.  There are more than 600 different species of oak.  Wisconsin has nine native oak species. Let’s look at Wisconsin’s oaks and how they are used in our daily lives.

First, oaks can be divided into two main groups: the red oak group and the white oak group.  Species in the red oak group typically have leaves with a “V” shaped sinus and lobe tips, with spiny bristles on the lobe tip.  In other words, the peaks and valleys around the leaf margin are pointed, like the bottom of the letter “V.”  Acorns in the red oak group take two growing seasons to mature.  In contrast, species in the white oak group typically have leaves with a “U” shaped sinus and lobe tips. The peaks and valleys around the leaf margin are rounded like the bottom of the letter “U.”  Acorns in the white oak group mature in one growing season.

The Northern Red Oak, Quercus rubra, is the most abundant oak in Wisconsin and is an important raw material for our sawmill industry.  The wood from the red oak is dense and has a pinkish color.  It is popular for flooring, furniture, moulding, millwork, and railroad ties.  Black oak, Quercus velutina, is another abundant oak, but its form is generally of a lower quality than the northern red oak.  As a result, the lumber produced from black oak has a higher proportion into the lower grades.  A third red oak is called the northern pin oak, Quercus elipsoidalis, grows on sandy soils. These three oaks can be found across the state. Another pin oak, Quercus palustris, is very rare in Wisconsin barely reaching the southern most counties. Finally, scarlet oak, Quercus coccinea, is found in a few counties in southern WI and is not a commercial species. It is important to note that all lumber produced from species in the red oak group are sold as red oak.  So as lumber, we don’t differentiate between species.

The white oak, Quercus alba, is an abundant Wisconsin oak in the white oak group.  The wood from the white oak is dense and has a light brown color.  It is popular for flooring, furniture, moulding, millwork, and railroad ties.  White oak lumber is also important for wine and whiskey barrels.  The wood cell structure is clogged by formations called tyloses.  These blockages prevent leakage from the barrels. If the same barrels were made using red oak, which lacks tyloses, they would surely leak.  Other common white oaks in Wisconsin are the Bur Oak, Quercus macrocarpa, and the Swamp White Oak, Quercus bicolor, which can all be used for white oak lumber. Finally, the Chinkapin Oak, Quercus muehlenbergii, is sparsely distributed in the southern part of the state.  Due to its rarity, it is not considered a commercial species.  In general, species in the white oak group and limited to the southern half of the state.  As with the red oak group, all lumber produced from species in the white oak group are sold as white oak lumber.  This is true across state lines as well. Bur Oak from Wisconsin and Chestnut Oak from Mississippi are all sold a white oak lumber.

From a wildlife perspective, oaks are important nesting trees for birds and small mammals. The flowers are an important food source for pollinating insects, while the acorn seed mast is an important food source for many animals including deer, bear, turkey, small mammals, and birds.

Oaks make up a large part of Wisconsin’s forests coming in second to the maples. Oaks are important lumber and pulpwood species and play an important role for humans as well as wildlife in our forests.