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Intro to Trees of Indiana: Bur Oak

The classic and trusted book "Fifty Common Trees of Indiana" by T.E. Shaw was published in 1956 as a user-friendly guide to local species.  Nearly 70 years later, the publication has been updated through a joint effort by the Purdue Department of Forestry and Natural Resources, Indiana 4-H, and the Indiana Department of Natural Resources, and reintroduced as "An Introduction to Trees of Indiana."

The full publication is available for download for $7 in the Purdue Extension Education Store. The field guide helps identify common Indiana woodlot trees. 

Each week, the Intro to Trees of Indiana web series will offer a sneak peek at one species from the book, paired with an ID That Tree video from Purdue Extension forester Lenny Farlee to help visualize each species as it stands in the woods. Threats to species health as well as also insight into the wood provided by the species, will be provided through additional resources as well as the Hardwoods of the Central Midwest exhibit of the Purdue Arboretum, if available. Line drawing of a bur oak leaf

This week, we take a look at the second of our oak varieties in Indiana, the Bur Oak or Quercus macrocarpa.

The bur oak has rounded lobes on the end of the leaves, which have deep sinuses and are very broad across the top. Leaves are typically dark green that turn yellow or brown in the fall.

The bark on bur oak is medium to dark gray in color with heavy ridges and plates, often so thick that it is often fire resistant and resistant to damage from burning. Bur oak may have terminal buds that include small hairs and resemble bear claws.  

The fruit of the bur oak is an acorn with a large cap that features a hairy fringe forming a burr along the outside edge. The acorns vary in size, but average one inch in length, and the cap covers half to two thirds of the acorn.Line drawing of a bur oak acorn

Bur oaks, which grow to 70-80 feet tall and up to five feet wide, are common in both bottomlands and prairie regions, and can tolerate many different sites. Bur oaks can be found in nearly any county and any habitat type in Indiana. The natural range of bur oak is the eastern Great Plains from the Dakotas to Ohio to the eastern Appalachians, except through the southeastern United States. The range also extends into southern Canada.

Lumber from the white oak group, which includes bur oak, is among the heaviest next to hickory, weighing in at 45 pounds per cubic foot. It is very resistant to decay and is one of the best woods for steam bending. Bur oak, however, is somewhat weaker than other species in the white oak group.

Wood from a bur oak is usually a darker brown in color than white oak and the wood grain sometimes has a scalloped appearance.

Lumber from the white oak group has been used for a variety of purposes including log cabins, ships, wagon wheels and furniture. White oak also is preferred for indoor decorative applications ranging from furniture, especially in churches, to cabinets, interior trim, millwork and hardwood flooring and veneers. It also may be used for barrel making.  

Its density and durability make white oak a favorite for industrial applications such as railroad ties, mine timbers, sill plates, fence posts and boards, pallets, and blocking, as well as industrial, agricultural and truck flooring.

The Morton Arboretum warns to prune oaks in the dormant season to avoid attracting beetles that may carry oak wilt. Bur oak can be affected by pests such as leaf galls and kermes scale as well as anthracnose, bacterial leaf scorch and powdery mildew. Bur oak blight also is a potential issue.  

Other Resources:
ID That Tree: Bur Oak
ID That Tree: White Oak Group
ID That Tree: Alternate Leaf Arrangement – Honey Locust/Bur Oak
Hardwood Lumber and Veneer Series: White Oak Group
Morton Arboretum: Bur Oak
Fifty Trees of the Midwest app for the iPhone, The Education Store
Native Trees of the Midwest, The Education Store
Shrubs and Woody Vines of Indiana and the Midwest, The Education Store
Investing in Indiana Woodlands, The Education Store
Forest Improvement Handbook, The Education Store
ID That Tree, Purdue Extension-Forestry & Natural Resources (FNR) YouTube playlist
Woodland Management Moment , Purdue Extension-FNR YouTube playlist

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