Native plant: The majestic bur oak helps support wildlife

Editor's note: Once a month, the OSU Extension master gardener's office of Franklin County profiles a plant that occurs naturally in central Ohio.

Native plant landscapes are increasingly promoted to provide much-needed habitat and food for insects, birds and other wildlife. A productive tree for such landscapes is the bur oak — Quercus macrocarpa. Growing to 60 to 80 feet high and wide in cultivated settings, this long-lived member of the white oak group bears a dense canopy that provides ample shade. Its broad, rounded crown is supported by substantial branches and a massive trunk.

Although bur oaks do not produce nectar-laden flowers for insects, these trees are larval hosts for numerous species of butterflies and moths. Larval caterpillars in turn are a critical food source for songbirds of all types, especially during the nesting and breeding season. Upon maturity, the tree produces large acorns that are a favored food for wood ducks, wild turkeys, rabbits, squirrels and other small mammals. Deer will browse unprotected sapling trees. 

Bur oak leaves have rounded lobes with deep sinuses, or indentations, at the bottom and shallow sinuses at the top, producing a distinctive guitar or cello shape. Leaves can grow to 12 inches long and half as wide. A lustrous deep green during the growing season, these leaves turn yellowish-brown in fall. Acorns are quite large — up to two inches in length — and are covered with a unique fringed cap that covers two-thirds or more of the nut. 

The wood of bur oak has been used for furniture, building construction, mine timbers, railroad ties and a host of utilitarian items. Early European settlers to this continent found this tree ample and useful. Even now it is the dominant woodland species in certain areas of the Great Lakes and central plains regions.

Because this tree produces a deep tap root, it can be difficult to transplant. Thus, container-grown plants are a good option. A slow to moderate grower, bur oak adds approximately 12 inches of growth annually. It might take several years for this tree to reach maturity, flower and produce acorns. It is adaptable to a variety of growing conditions, and is one of the better oaks for alkaline soils.

Bur oak is native to a wide swath of the central and northern United States and southern Canada. It is found in many environmentss, ranging from bottomland forests to prairies and drier elevations. In moist soils, the tree can reach 100 feet or more, while in drier locales it is usually much smaller, almost shrubby. Bur oak is as variable as it is adaptable.

A few cultivars of bur oak are available. ‘Urban Pinnacle’ has a more upright, pyramidal form with very small acorns. The deep-green foliage of ‘Cobblestone’ is resistant to mildew and anthracnose. In the wild, bur oak will combine with other white oak species to produce natural hybrids.

Growing conditions

Hardiness zones: 3 to 9

Sun: full sun is best

Water: adaptable; tolerates wet conditions and drought

Soil: quite adaptable; prefers moist, acidic soils

Maintenance: prune during winter months only to prevent oak wilt infections

Propagation: by seed

Pests and diseases: subject to several, but seldom serious