Quercus macrocarpa, the bur oak or burr oak, is a species of oak tree native to central and eastern North America. It is in the white oak section, Quercus sect. Quercus, and is also called mossycup oak, mossycup white oak, or scrub oak. The acorns are the largest of any North American oak (thus the species name macrocarpa, from Ancient Greek "large" and "fruit"), and are important food for wildlife.
Description
Quercus macrocarpa is a large deciduous tree growing up to , rarely , in height, and is one of the most massive oaks with a trunk diameter of up to . It is one of the slowest-growing oaks, with a growth rate of per year when young. However, one source states that a well-established tree can grow up to per year. A 20-year-old tree will be about tall if grown in full sun. Naturally occurring saplings in forests will typically be older. Bur oaks commonly live to be 200 to 300 years old, and may live up to 400 years. The bark is gray with distinct vertical ridges.
Bur oaks primarily grow in a temperate climate on the western oak–hickory forested regions in the United States and into Canada. It commonly grows in the open, away from dense forest canopy. For this reason, it is an important tree on the eastern prairies, often found near waterways in otherwise more forested areas, where there is a break in the canopy. It is drought resistant, possibly because of its long taproot. At the end of the growing season, a one-year sapling may have a taproot deep and a lateral root spread of . The bur oak shows a preference for limestone or other calcareous soils. are fire-tolerant because of their thick bark. One of the bur oak's most common habitats, especially in Midwestern United States, is the oak savanna, where fires often occurred in early spring or late fall. Without fires, bur oak is often succeeded by other tree and shrub species that are more shade-tolerant. Older bur oaks may survive in dense woodlands for 80 years, until they are weakened by wood-rot fungi in the lower branches killed by shade, and by 100 to 110 years, they are often snapped by wind storms.
Uses
thumb|Wood showing growth rings
The wood of Quercus macrocarpa is commercially valuable; it is durable, used for flooring, fence posts, cabinets, and barrels. The acorns can be eaten boiled and raw. Native Americans have used the astringent bark to treat wounds, sores, rashes, and diarrhea.
Culture
Many places are named after the burr oak, such as Burr Oak State Park in Ohio, the cities of Burr Oak, Iowa and Burr Oak, Kansas, and the village of Burr Oak, Michigan. Burr Oaks (1947) is a volume of poetry by Richard Eberhart.