Bur oak
Quercus macrocarpa, Hardiness : Zone 3b
Categories
Nut tree or shrub, Ornamental tree
Availability
1 year old, 10cm high, naked roots 7.00$
Features
Height X Width
20.0m X 20.0m
Foliage
-
Flowering
-
Edible parts description
Edible acorn
Resistances
-
Sun exposure
Full sun
Soil type
-
Edible parts
Seeds
Pollination
Needs another plant nearby to bear fruits
Images
Click to see full size
Description, from Wikipedia

Quercus macrocarpa is a large deciduous tree growing up to 98 ft (30 m), rarely 160 ft (50 m), in height, and is one of the most massive oaks with a trunk diameter of up to 10 ft (3 m); reports of taller trees occur, but have not been verified. It is one of the slowest-growing oaks, with a growth rate of 1 ft (30 cm) per year when young. However, other sources state that a bur oak tree that is planted in the ground grows up to 3 ft (91 cm) per year. A 20-year-old tree will be about 20 ft (6 m) tall if grown in full sun. Naturally occurring saplings in forests will typically be older. Bur oaks commonly get to be 200 to 300 years old, and may live up to 400 years. The bark is gray with distinct vertical ridges.

The leaves are 2 34–6 in (7–15 cm) long and 2–5 in (5–13 cm) broad, variable in shape, with a lobed margin. Most often, the basal two-thirds is narrower and deeply lobed, while the apical third is wider and has shallow lobes or large teeth. The flowers are greenish-yellow catkins, produced in the spring. The acorns are very large, 1–2 in (2.5–5 cm) long and 341 12 in (2–4 cm) broad, having 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.

Bur oak is sometimes confused with overcup oak and the white oak, Quercus alba. It hybridizes with both these species.

The acorns are the largest of any North American oak (thus the species name macrocarpa, from Ancient Greek μακρός makrós "large" and καρπός karpós "fruit"), and are an important wildlife food; American black bears sometimes tear off branches to get them. However, heavy nut crops are borne only every few years. In this evolutionary strategy, known as masting, the large seed crop every few years overwhelms the ability of seed predators to eat the acorns, thus ensuring the survival of some seeds. Other wildlife, such as deer and porcupine, eat the leaves, twigs and bark. Cattle are heavy browsers in some areas. The bur oak is the only known foodplant of Bucculatrix recognita caterpillars.

Bur oaks primarily grow in a temperate climate on the western oak-hickory forested regions in the US and into Canada.

The wood when sawn transversely shows the characteristic annual rings formed by secondary thickening.