With its distinct fruit, the acorn, and spiraling leaf pattern, the Oak tree is easily identified. However these similarities are only a few, in a diverse species whose terrain spans from cool to tropical latitudes. A member of the Beech Family and the genus Quercus, the oaks comprise a vast group, with approximately 450 cataloged species throughout the world. There is dispute as to the exact number recognized by horticulturalist trades as there is a high rate of hybridization. They are characterized by alternating, simple, deciduous or evergreen leaves with lobed, toothed, or entire margins, and are primarily trees, however there are some shrubs, mostly dependent upon habitat and growing conditions. Most, but not all, prefer deep, moist, well-drained soils, which are often fairly acidic and nutrient-deficient.
Primarily plants of the Northern Hemisphere, oaks are found in the temperate and tropical regions of southeastern Asia, Central and South America. Between 75 and 80 of these species are native to North America, with about half as trees. The flowers are called catkins, a narrow cluster with inconspicuous petals, which blooms in mid-spring. Interestingly it is this wind-pollination that allows the oaks to interbreed fairly freely where their canopies overlap, the offspring of which generally displaying traits of both parents. From the borders of swamps to dry uplands, the oak tree can be found in a variety of shapes and habitats.
The oaks of North America are distinguished into two groups by easily identifiable characteristics in bark, leaf, and acorn. The primary difference between these groups is the length of time for an acorn to mature, one season or two. The annual-fruiting trees have leaves with rounded lobes and generally pale bark. These are the White Oaks. The Black Oaks are biennial fruiting, whose leaves have lobes that end in angles and bristly tips. Their bark is also darker, as name suggests, although this should not be used as the only determining characteristic.
Quercus alba, White Oak
An important economic tree since colonial times, this species of oak was once extensively used in shipbuilding and is currently the major source of wood for cooperage. It is also highly valued in the construction of furniture, flooring, and caskets. Slow-growing and difficult to transplant, this long-lived tree reaches an average height of 100 ft (30 m) during its 600 year life span. This species tends to establish itself after disturbances, such as fire, however it is slowly being replaced as seedlings cannot persist in the shade of the canopy. With a wide, straight trunk, this tree grows well in both forested and open conditions. A dominant tree in many hardwood plant communities it can be found from southeastern Quebec to Maine, down into northwestern Florida and west into Texas, anywhere from sea level to 5,900 ft (1,800 m). It grows best on deep, well-drained and moist loams, but can be found on a variety of soils, including gravelly and rocky terrain provided they are also well-drained where roots can grow deep. The pale brown wood distinctly shows narrow annual rings comprised of two bands. A coarse and porous “spring wood,” followed by a narrower band of find, close-grained summer growth.
Quercus rubra, Northern Red Oak
Important for timber production in the United States, the Northern Red Oak is the only member of the Red Oak-Black Oak subgenus to be used commercially. This oak tree with bristly lobed leaves which turn red in the fall is often found in pure strands and common in many forested habitats. This is tree is native to the northern part of the US and ranges from Oklahoma to Georgia. While this tree grows best on deep, fertile, well-drained but moist, and fine-textured soils, it can be found in a variety of other conditions. One of the fastest growing oaks, this tree usually attains heights of 90 ft (27 m), although it may reach 160 ft (49 m) depending. Under optimal growing conditions, a 10-year-old tree can be 15-20 ft tall. This characteristic is a boon for the lumber industry as its wood is highly prized. Red oaks are a generally long-lived species, up to 500 years, as such they persist in well-established forests despite being only moderately shade-tolerant.
Quercus macrocarpa, Bur Oak
Though slightly darker, this wood is classified with the White Oak and contains the same desirable qualities that are pleasing to the eye. A rugged and ragged tree comparatively, the wood is tough and strong, durable wherever needed. This tenacious species has a range from Nova Scotia to Montana, growing in long tracks, and thrives in the arid soil of Nebraska and Dakota. Often found near waterways and an integral part of the eastern prairie ecology, this tree typically grows away from the forest canopy. One of the most massive oaks with a trunk diameter of up to 10 ft (3 m), this deciduous tree quite easily grows to 100 ft (30 m). It is one of the slowest growing oaks, with a rate of 1 ft (30 cm) when young and commonly lives to be between 200 and 300 years old. The leaves are 3-6 in long and about as broad, with a lobed margin. The acorns produced by the Bur Oak are the largest of any North American oak. Suited to urban conditions, this tree is one of the most fire-tolerant of the species.
Quercus prinus, Chestnut Oak
Unlike other White Oaks, the bark of this tree is dark in colour and deeply fissured. This richness is caused by a store of tannin in the bark and is often used to tan leather. Heavy and durable in soil, this close-grained wood is adaptable and well suited for outdoor applications. The leaves of this oak are 5 to 9 in long, coarsely toothed and appear in outline and size like those of the Chestnut tree. Native to the eastern United States, this is an important ridge-top tree, from southern Maine to central Mississippi. In the appropriate growing conditions that allow for a long straight trunk, the wood of this tree can be very valuable. However as a consequence of its generally dry habitat and ridge-top exposure these trees typically reach a height of 60-70 ft (18-22 m).
Quercus platanoides, Swamp White Oak
One of the more important White Oaks for lumber production, this lowland tree is most common in western New York and northern Ohio, where it reaches its largest size. It can also be found from Quebec to Kansas and thrives in a variety of temperatures and habitats. It prefers to stand in wet ground, and is often found in swamps, although not where flooding is permanent. Typically growing 65-80 ft (20-25 cm) tall, with a trunk diameter of 2-4 ft, this tree can reach 300 years in age. The leaves are broad and shallowly lobed, with five to seven lobes on each side. In autumn they turn yellow-brown and sometimes reddish. Lumber from this oak is light to medium brown, with some variation in colour. This hard, durable species has a fairly coarse grain and has a high resistance to decay.
Quercus garryana, Pacific Post Oak
The only native oak in British Columbia, this trees terrain follows the valleys of the Coast Range into the Santa Cruz Mountains. Drought tolerant and fire resistant, this variety grows nearly 100 ft (30 m) high with a broad, compact crown, or as a shrub depending on conditions. The leaves are dark green and coarsely lobed turning the occasional bright scarlet in autumn. Employed in the manufacture of wagons and furniture, from ship-building to cooperage, this wood is hard, strong, tough, and close-grained.
Quercus agrifolia, California Oak
Also called the Coast Live Oak, this Evergreen Oak (highly variable and often shrubby), is native to the California Floristic Province. It grows west of the Sierra Nevada from Mendocino County, California and south to northern Baja California in Mexico. It is classified in the red oak section (Quercus sect. Lobatae). This species is commonly sympatric with Canyon Live Oak, and the two may be hard to distinguish because their spinose leaves are superficially similar. Coast Live Oak is the only California native oak that actually thrives in the coastal environment, although it is rare on the immediate shore; it enjoys the mild winter and summer climate afforded by ocean proximity, and it is somewhat tolerant of aerosol-borne sea salt. The coastal fog supplies relief from the rainless California summer heat.
Quercus robur, Pedunculate Oak, French Common Oak
One of two predominant species in the region, this tree can be found in long stands across Europe, from Ireland through France to the Caucasus and north to Scandinavia. Even 500 years ago, one third of Great Britain was still covered in oak forests. Flowering takes place in mid spring and its acorns, grown on long stalks amidst small and bunched leaf clusters, ripen by the following autumn. It is reference to these stalks that give this oak its unique common name. Reaching heights of 50 ft (15 m), these trees grow long and straight with trunk diameters up to 6 ft. When grown in the open they have broad and spreading, angular branches that form the crown. They are fairly hearty and do well transplanted, given appropriate care and conditions, and thrive in any fertile, well-drained soil, with sun or partial shade. A popular tree for English parks and often-romanticized in literature, these trees can easily exceed 500 years of age. The English Oak is planted for forestry, and produces a long-lasting and durable heartwood, which is highly prized for interior and furniture work.
English Brown Oak
From the coronation throne of the English monarchy to American courthouses, English Brown Oak is as durable as it is beautiful. While location and mineral content often affect not only a trees growth but also its appearance, the fungus Fistulina hepatica causes this unique colouration in European species of oak. Commonly known as beefsteak fungus, it attacks susceptible trees of both Q. robur and Q. patraea, eventually turning the heartwood a rich butternut brown with distinctive markings. This affects approximately 1 in every 500 oaks across Europe, and despite what the common name suggests, the best examples often come from forests in Germany. The drying process can be a bit tedious, however once it is finished the fungus is completely dead, leaving the desirable heartwood sturdy and intact. High in tannins, which can corrode some metal fasteners, this wood is moderately decay resistant when used in outdoor projects. Its fine grain is also easy to work, with both hand and power tools.
Quercus petraea, Sessile Oak, French White Oak, Durmast Oak, Spessart Oak
A large, deciduous tree, the Sessile Oak grows from 65-130 ft and is similar to Q. robur in growth habits, with which it overlaps extensively in range, although extending further into France. There are however, significant botanical differences, larger stalked leaves, which are dispersed evenly throughout the branches and the stalkless (sessile) acorns, from which one of its common names is derived. This tree also tends to occur more abundantly in upland locations, nearly 1000 ft (300 m) above sea level, with higher rainfall and comparatively shallow, acidic, and sandy soils. In France these trees grow primarily in the forests of Allier, Limousin, Nevers, Troncais and Vosges and in Belgium.
These trees often exceed a couple of centuries in age. The wood, traditionally used for shipbuilding, is important for a number of applications, particularly timber framing and oak barrels.
The finest “French Oak” actually comes from the Spessart forest in Germany, where conditions are favorable for the growth of magnificent white oak trees. This forest has been tended for over 150 years, meticulously allowing for oak protection and growth as it takes a minimum of 300 years before a Spessart Oak is mature enough to harvest. The average growth of these trees is 20 to 30 growth rings per inch, creating a very fine tight-grained texture. The soil in Spessart is predominately red sandstone, with no minerals to stain the wood, and is well drained. Only three cubic meters from each hectare are harvested a year to prevent from degrading the resource. It is this long range view of forestry that allows Spessart to continue to provide a high quality, albeit limited resource for lumber.
Quercus mongolica, Mongolian Oak, Japanese Oak
This species of oak is native to most of eastern Asia and spans a vast region including both of its namesakes, most of northern and central China, and other small islands of the region. As its terrain suggests, this species of oak can withstand temperatures down to 5°F (-15°C) and prefers fertile, moist, well-drained soil, and like most oaks, is only partially shade tolerant. The dark-green leaves are 8 in (20 cm) or more and are borne in dense clusters at the ends of branches, which can grow to a span of 50 ft (15 m). The rounded crown of branches adorns sturdy trunks that can reach 70 ft (20 m) in forest conditions. Japanese Oak is a moderately light fine-grained wood and used in a number of applications.
The usefulness of the oak is well known and its praises have been sung as far back as the mid-400s B.C.E . As Heroditus, the father of ancient history recorded, “oak trees...have within their boughs, the gift of prophecy.” Purportedly, at least, or perhaps it is their versatility and breadth, not only of terrain but subtlety of species, that lends itself to the majesty of the oak. The oak is a common symbol of strength and endurance and is the national tree of many countries and many coat-of-arms. The oldest of these trees are around 1500 years old, found in both Europe and the Americas. One such example, nicknamed Kongeegen (King Oak), in Denmark is estimated to be between 1500 and 2000 years. Even the Latin name Quercus is in reference to its usefulness. From the word,” to eat”, we are reminded not only of its importance to small woodland creatures, but also of the indigenous foragers who included acorns as a staple of their diet.