A massive long-lived oak with thick fire-resistant bark and the largest acorns of any North American oak (up to 2 inches across). Once a defining species of midwestern oak savannas.

Also called: Mossycup Oak, Burr Oak

Native status: Native to central and eastern US

§ Quick facts

SizeMature height 21–30 m (70–100 ft); trunk diameter 1.5–3.0 m
WeightN/A
Lifespan200–400 years; some over 400
OrderFagales
FamilyFagaceae

§ Encyclopedia

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, and are important food for wildlife.

Source: Wikipedia — Quercus macrocarpa Licensed under CC BY-SA 4.0

§ Identification

Field marks. Large slowly-growing oak with deeply furrowed gray bark; corky-winged twigs; large lobed leaves with deeply notched middle; massive fringed-cup acorns.

Similar species. Swamp White Oak (similar leaves; wetland habitat). Post Oak (smaller acorns, different leaf shape). Chinquapin Oak (different leaf shape, smaller acorns).

Voice. N/A

§ Diet & behavior

Diet. N/A — photosynthesis

Behavior. Quintessential oak savanna species. Thick fire-resistant bark (up to 15 cm) protects from prairie fires that killed most other trees, allowing bur oaks to persist as scattered trees across the eastern tallgrass and oak savanna landscapes. Acorns are the largest of any North American oak — up to 5 cm long, with deep fringed cups. Acorns germinate quickly after falling; deep taproot allows seedlings to survive drought and fire.

§ Range

Central US and southern Canada, especially edges of prairie and oak savanna

§ Habitat

Oak savannas, prairie edges, riparian forests, fire-prone landscapes

§ Threats

Loss of oak savanna habitat, fire suppression overgrowing savannas, urban development.

§ Conservation status

According to the IUCN Red List, the bur oak is currently classified as Least Concern.

§ What helps

Support prescribed-fire savanna management. Plant bur oaks (drought-tolerant urban trees). Don't over-tidy fallen acorns.

Support our work More ways to help

§ Further reading

§ Sources cited

  • USDA Plants Database
  • The Nature Conservancy oak savanna program
  • USDA Forest Service Silvics Manual
  • IUCN Red List 2017