Burr Oak

Quercus macrocarpa, the Bur Oak, sometimes spelled Burr Oak, is a species of oak in the white oak section Quercus sect. Quercus, native to North America in the eastern and midwestern United States and south-central Canada. This plant is also called Mossycup oak and Mossycup white oak.

It is a large deciduous tree growing up to 30 m (100 ft), rarely 37 m (120 ft), in height, and is one of the most massive oaks with a trunk diameter of up to 3 m (10 ft); reports of taller trees occur, but have not been verified. It is one of slowest-growing oaks, with growth rate of 30 cm (1 ft) per year when young. A 20-year-old tree will be about 6 m (20 ft) tall. It commonly lives to be 200 to 300 years old, and may become significantly older. The bark is a medium gray and somewhat rugged.

The leaves are 7–15 cm (3–6 in) long and 5–13 cm (2–5 in) broad, variable in shape, with a lobed margin. Most often, the basal 60% is narrower and deeply lobed, while the apical 40% is wider and has shallow lobes or large teeth. The flowers are greenish-yellow catkins, produced in the spring. The acorns are very large, 2–5 cm (0.8–2 in) long and 2–4 cm (0.8-1.5 in) broad, with a large cup that wraps much of the way around the nut, with large overlapping scales and often a fringe at the edge of the cup.