Quercus rubra, the northern red oak or common red oak, is an oak tree in the red oak group (Quercus section Lobatae). It is a native of North America, in the eastern and central United States and southeast and south-central Canada. It has been introduced to small areas in Western Europe, where it can frequently be seen cultivated in gardens and parks. It prefers good soil that is slightly acidic. Often simply called red oak, northern red oak is so named to distinguish it from southern red oak (Q. falcata), also known as the Spanish oak.
Description In many forests, Quercus rubra grows straight and tall, to 28 metres (92 feet), exceptionally to 43 m (141 ft) tall, with a trunk of up to 50–100 centimetres (20–39 inches) in diameter. Open-grown trees do not get as tall, but can develop a stouter trunk, up to 2 m (6+1⁄2 ft) in diameter. It has stout branches growing at right angles to the stem, forming a narrow round-topped head. Under optimal conditions and full sun, northern red oak is fast growing and a 10-year-old tree can be 5–6 m (16–20 ft) tall. Trees may live up to 400 years; a living example of 326 years was noted in 2001. Northern red oak is easy to recognize by its bark, which features ridges that appear to have shiny stripes down the center. A few other oaks have bark with this kind of appearance in the upper tree, but the northern red oak is the only tree with the striping all the way down the trunk. As with most other deciduous oaks, leafout takes place in spring when day length has reached 13 hours, tied entirely to the photoperiod regardless of air temperature. As a consequence (see below), in cooler regions, northern red oaks often lose their flowers to late spring frosts, resulting in no seed crop for the year. The catkins and leaves emerge at the same time. The acorns develop on the tree for two growing seasons and are released from the tree in early October, and leaf drop begins when day length falls under 11 hours. The timing of leafout and leaf drop can vary by as much as three weeks in the northern and southern US. Seedlings emerge in spring when soil temperatures reach 21 °C (70 °F).
Bark: Dark reddish gray brown, with broad, thin, rounded ridges, scaly. On young trees and large stems, smooth and light gray. Rich in tannin. Branchlets slender, at first bright green, shining, then dark red, finally dark brown. Bark is brownish gray, becoming dark brown on old trees. Wood: Pale reddish brown, sapwood darker, heavy, hard, strong, coarse-grained. Cracks in drying, but when carefully treated could be successfully used for furniture. Also used in construction and for interior finish of houses. Sp. gr., 0.6621; weight of cu. ft., 41.25 lbs. Winter buds: Dark chestnut brown (reddish brown), ovate, acute, generally 6 mm (1⁄4 in) long Leaves and acorns: Alternate, oblong-ovate to oblong, five to ten inches long, four to six inches broad; seven to eleven lobes tapering gradually from broad bases, acute, and usually repandly dentate and terminating with long bristle-pointed teeth; the second pair of lobes from apex are largest; midrib and primary veins conspicuous. Lobes are often less deeply cut than most other oaks of the red oak group. Leaves emerge from the bud convolute, pink, covered with soft silky down above, coated with thick white tomentum below. When full grown are dark green and smooth, sometimes shining above, yellow green, smooth or hairy on the axils of the veins below. In autumn they turn a rich red, sometimes brown. Often the petiole and midvein are a rich red color in midsummer and early autumn, though this is not true of all red oaks. The acorns mature in about 18 months after pollination; solitary or in pairs, sessile or stalked; nut oblong-ovoid with broad flat base, full, with acute apex, one half to one and one-fourth of an inch long, first green, maturing nut-brown; cup, saucer-shaped and shallow, 2 cm (3⁄4 in) wide, usually covering only the base, sometimes one-fourth of the nut, thick, shallow, reddish brown, somewhat downy within, covered with thin imbricated reddish brown scales. Its kernel is white and very bitter. Red oak acorns, unlike the white oak group, display epigeal dormancy and will not germinate without a minimum of three months' exposure to temperatures below 4 °C (40 °F). They also take two years of growing on the tree before development is completed.
Distribution and habitat The species grows from the north end of the Great Lakes, east to Nova Scotia, south as far as Georgia, Mississippi, Alabama, and Louisiana, and west to Oklahoma, Kansas, Nebraska, and Minnesota. It grows rapidly and is tolerant of many soils and varied situations, although it prefers the glacial drift and well-drained borders of streams. In the southeastern United States, it is frequently a part of the canopy in an oak-heath forest, but generally not as important as some other oaks. Northern red oak is the most common species of oak in the northeastern US after the closely related pin oak (Q. palustris). The red oak group as a whole are more abundant today than they were when European settlement of North America began as forest clearing and exploitation for lumber much reduced the population of the formerly dominant white oaks.
Reproduction "Northern red oak (Quercus rubra L.) is monoecious, dichogamous, wind-pollinated, and self-incompatible". Pollination occurs in the first growing season, but fertilization and acorn maturation occur during the second growing season.
Ecology
Over the last few decades, the northern red oak has dealt with several environmental factors, mainly disease, predation by insects, and limited opportunities for dispersal. These stresses have impacted the species' ability to proliferate in both the Northeast and Europe. The various environmental responses observed in Quercus rubra across several temperate environmental conditions have allowed for it to serve as a model organism for studying symbiotic relationships, dispersal, and habituation between tree species.
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