Tree Spotlight: Quercus macrocarpa


Quercus macrocarpa

Trade Name: Bur oak

General distribution: Widespread in the Atlantic coastal plain from New Brunswick, Canada to North Carolina; west as far as Alberta, Canada, eastern Montana, Wyoming and northeastern New Mexico; vast majority are found in the eastern Great Plains, the Mississippi/ Hampton Roads/Ohio valleys and the Great Lakes region.

Wood Value: High quality and is almost always marketed as “white oak.”

Other uses: Is often cultivated by plant nurseries for use in gardens, parks and on urban sidewalks.

Family: Fagaceae

Value for rehabilitation of disturbed sites: Survival and persistence have been reported on revegetated mine sites. Can be established from seed or seedlings and grows well with herbaceous species, but isn’t recommended for soils with a pH less than 4.

Seasonal development: Throughout its range, flowers sometime between April and early June. Acorns are produced in the same year as the flowers. Acorns fall as early as August and as late as November.

General botanical characteristics:

  • Grows as a large, spreading tree up to 130 feet tall (growth form and size can vary by site).
  • Branches in the upper portion of the crown are ascending; in the lower crown, branches are larger and horizontal.
  • The trunks of mature trees have thick, deeply grooved bark and may measure 8.5 feet in diameter.
  • In the western part of its range on exposed, harsh sites, grows as a small tree or shrub and may produce crooked, gnarled branches.
  • It’s a long-lived tree — it’s common to find remnant trees that are 300 to 400 years old. In a savanna in Kentucky, a bur oak was an estimated 440 years old.
  • The sizes and shapes of leaves are variable, but generally leaves are deeply lobed and large, up to 12 inches long and about half as wide. Shallowly lobed leaves may occur on bur oak sprouts or deeply shaded branches and small leaves are common in the northern Great Plains.
  • Leaves are deep green and shiny above and coated with white hairs below.
  • Produces male flowers in 3- to 4-inch long catkins and female flowers are solitary or in clusters of up to four.
  • Typically produces extensive root systems with wide-spreading laterals and a deep taproot.

Management considerations:

  • Is a conservation concern in Canada and several bur oak communities in the Plains region are considered “imperiled.”
  • Savannas are important for lepidopteran communities. On Iowa’s Neal Smith National Wildlife Refuge, smaller forests lacking a prominent bur oak component supported 65 fewer species of moths than larger, bur oak-dominated savanna remnants.
  • Some studies suggest that bur oak establishment is best during drought conditions or on dry, open sites, while other studies indicate that establishment is best on mesic sites.

Source: U.S. Forest Service (FS.Fed. US); North American Plant Atlas

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