OAK (Anglo-Saxon, äc or asc), a word found, variously modified, in all Germanic languages, and applied to plants of the genus Quercus, a well-marked section of the natural order Corylaceae (Cupuliferae of De Candolle), including some of the most important timber trees of the north temperate zone. All the species are arborescent or shrubby, varying in size from the most stately of forest trees to the dwarfish bush. Monoecious, and bearing their male flowers in catkins, they are readily distinguished from the rest of the Cupuliferous family by their peculiar fruit, an acorn or nut, enclosed at the base in a woody cup, formed by the consolidation of numerous involucral bracts developed beneath the fertile flower, simultaneously with a cup-like expansion of the thalamus, to which the bracteal scales are more or less adherent. The ovary, three-celled at first, but becoming one-celled and one-seeded by abortion, is closely invested by the perianth, toothed on the margin, and adherent below; the male flowers are in small clusters on the usually slender and pendent stalk, forming an interrupted catkin; the stamens vary from six to twelve. The alternate leaves are more or less deeply sinuated or cut in most of the species, but in some of the deciduous and many of the evergreen kinds are nearly or quite entire on the margin. The oaks are widely distributed over the temperate parts of Europe, Asia, North Africa, and North America. In the western hemisphere they range along the Mexican highlands and the Andes far into t.hp. ironies, while in the Old World the genus, well represented in the Himalayas and the hills of China, exists likewise in the peninsula of Malacca, in Java, and in some other islands of the archipelago, several species occurring in the Moluccas and Borneo. On the ...mountains of Europe and North America they grow only at moderate elevations, and none approach the arctic circle. The multitude of species and the many intermediate forms render their exact limitation difficult, but those presenting sufficiently marked characters to justify specific rank probably approach 300 in number.
The well-known Q. Robur , one of the most valued of the genus, and the most celebrated in history and myth, may be taken as a type of the oaks with sinuated leaves. Though known in England, where it is the only indigenous species, as the British oak, it is a native of most of the milder parts of Europe, extending from the shores of the Atlantic to the Ural; its most northern limit is attained in Norway, where it is found wild up to lat. 63°, and near the Lindesnaes forms woods of some extent, the trees occasionally acquiring a considerable size. In western Russia it flourishes in lat. 60°, but on the slope of the Ural the 56th parallel is about its utmost range. Its northern limit nearly coincides with that of successful wheat cultivation. Southwards it extends to Sardinia, Sicily, and the Morea. In Asia it is found on the Caucasus, but does not pass the Ural ridge into Siberia. In Britain and in most of its Continental habitats two varieties exist, regarded by many as distinct species: one, Q. pedunculata, has the acorns, generally two or more together, on long stalks, and the leaves nearly sessile; while in the other, Q. sessiliflora, the fruit is without or with a very short peduncle, and the leaves are furnished with well-developed petioles. But, though the extreme forms of these varieties are very dissimilar, innumerable modifications are found between them; hence it is more convenient to regard them as at most sub-species of Q. Robur. The British oak is one of the largest trees of the genus, though old specimens are often more remarkable for the great size of the trunk and main boughs than for very lofty growth. The spreading branches have a tendency to assume a tortuous form, owing to the central shoots becoming abortive, and the growth thus being continued laterally, causing a zigzag development, more exaggerated in old trees and those standing in exposed situations; to this peculiarity the picturesque aspect of ancient oaks is largely due. When standing in dense woods the trees are rather straight and formal in early growth, especially the sessile-fruited kinds, and the gnarled character traditionally assigned to the oak applies chiefly to its advanced age. The broad deeply-sinuated leaves with blunt rounded lobes are of a peculiar yellowish colour when the buds unfold in May, but assume a more decided green towards midsummer, and eventually become rather dark in tint; they do not change to their brown autumnal hue until late in October, and on brushwood and saplings the withered foliage is often retained until the spring. The catkins appear soon after the young leaves, usually in England towards the end of May; the acorns, oblong in form, are in shallow cups with short, scarcely projecting scales; the fruit is shed the first autumn, often before the foliage changes.
Vast oak forests still covered the greater part of England and central Europe in the earlier historic period; and, though they have been gradually cleared in the progress of cultivation, oak is yet the prevailing tree in most of the woods of France, Germany, and southern Russia, while in England the coppices and the few fragments of natural forest yet left are mainly composed of this species. The pedunculated variety is most abundant in the southern and midland counties, the sessile-fruited kinds in the northern parts and in Wales, especially in upland districts; the straighter growth and abundant acorns of this subspecies have led to its extensive introduction into plantations. The name of “durmast” oak, originally given to a dark-fruited variety of Q. sessiliflora in the New Forest, has been adopted by foresters as a general term for this kind of oak; it seems to be the most prevalent form in Germany and in the south of Europe. A variety of the sessile oak with sweet acorns appears to be the Q. Esculus of some writers. Many of the ancient oaks that remain in England may date from Saxon times, and some perhaps from an earlier period; the growth of trees after the trunk has become hollow is extremely slow, and the age of such venerable giants only matter of vague surmise. The celebrated Newland oak in Gloucestershire, known for centuries as “the great oak,” was by the latest measurement 47∣ feet in girth at 5 feet from the ground. The Cowthorpe oak, standing (a ruin) near Wetherby in Yorkshire, at the same height measures 38J feet, and seems to have been of no smaller dimensions when described by Evelyn two centuries ago; like most of the giant oaks of Britain, it is of the pedunculate variety. The preservation of these old trees has been in past times largely due to the survival of the reverence in which the oak was held by Celt and Saxon,—a feeling which seems to have been shared by several Aryan races. The great regard paid to the oak probably originated in the value attached to its timber and fruit; the largest and most durable of European trees, its wood was looked upon as the most precious produce of the forest. With both Greek and Roman it was the favourite timber for house, bridge, and ship building; and the furrowed columns with spreading base that upheld their stone-built temples of historic age seem to indicate the oak-trunk as their archaic prototype. The tree was not in less esteem among the Teutonic nations; the long ships Of the Northmen were hewn from the same “heart of oak” of which the war-ships of England were until lately constructed. The Anglo-Saxons employed oak timber not only for their dwellings and their fleets but occasionally for more sacred architecture,—the church till recently standing at Greenstead in Essex, and supposed to have been erected in the 10th century, was wholly formed of oak trunks roughly squared. The few ancient timber mansions still existing in England are generally built entirely of oak, which in many cases remains sound after the lapse of several hundred years, sometimes outlasting the brick and stone with which the structures have been repaired. The great oak woods that in early days covered the larger part of Britain had in Tudor times become so reduced that an Act was passed in the reign of Henry VIII. to enforce their preservation, and by the end of the 16th century oak planting became common. At present large quantities of timber are still obtained from hedgerows and copsewoods; but, although some attempts have been made to renew the royal forests, much of the oak timber employed in Britain is imported from abroad. Many of the Continental woods are failing to produce their former supply the large quantity still obtained from the port of Memel, and formerly drawn from Prussia and nearer Poland, is now brought thither from the distant forests of the Dnieper and the Don.
The wood of the British oak, when grown in perfection, is the most valuable produced in temperate climates. The heart-wood varies in colour from dark brown to pale yellowish - brown; hard, close-grained, and little liable to split accidentally, it is, for a hard wood, easy to work. Under water it excels most woods in durability, and none stand better alternate exposure to drought and moisture, while under cover it is nearly indestructible as long as dry-rot is prevented by free admission of air. Its weight varies from 48 to about 55 lb the cubic foot, but in very hard slowly-grown trunks sometimes approaches 60 ft>. The sap-wood is lighter and much more perishable, but is of value for many purposes of rural economy. The relative qualities of the two varieties have been the frequent subject of debate, the balance of practical testimony seeming to establish the superiority of Q. pedunculata as far as durability in water is concerned; but when grown under favourable circumstances the sessile oak is certainly equally lasting if kept dry. The wood of the durmast oak is commonly heavier and of a darker colour, hence the other is sometimes called by woodmen the white oak, and in France is known as the “chêtie blanc.” The oak of Britain is still in great demand for the construction of merchant shipping, though teak has become in some measure its substitute, and foreign oak of various quality and origin largely takes its place. Its great abundance of curved trunks and boughs rendered the oak peculiarly valuable to the shipwright when the process of bending timber artificially was less understood; the curved pieces are still useful for knees. The younger oaks are employed by the carpenter, wheelwright, waggon-builder, and for innumerable purposes by the country artisan. The most durable of fences are those formed of small oaks, split lengthwise by the wedge into thin boards. The finely-grained heart-wood is sought by the cabinetmaker for the manufacture of furniture, and high prices are often given for the gnarled and knotted portions of slowly-grown trees, to be sawn into veneers. Oak was formerly largely used by wood-carvers, and is still in some demand for those artists, being harder and more durable than lime and other woods that yield more readily to the sculptor’s tool. Oak was thus applied at a very early date; the shrine of Edward the Confessor, still existing in the abbey at Westminster, sound after the lapse of 800 years, is of darkcoloured oak-wood. The wood, of unknown age, found submerged in peat-bogs, and of a black hue, is largely used in decorative art under the name of “bog-oak.”
The oak grows most luxuriantly on deep strong clays, calcareous marl, or stiff loam, but will flourish in nearly any deep well-drained soil, excepting peat or loose sand; in marshy or moist places the tree may grow well for a time, but the timber is rarely sound; on hard rocky ground and exposed hillsides the growth is extremely slow and the trees small, but the wood is generally very hard and durable. The oak will not bear exposure to the full force of the sea gale, though in ravines and on sheltered slopes oak woods sometimes extend nearly to the shore. The cultivation of this tree in Europe forms one of the most important branches of the forester’s art. It is frequently raised at once by sowing the acorns on the ground where the trees are required, the fruit being gathered in the autumn as soon as shed, and perfectly ripe seeds selected; but the risk of destruction by mice and other vermin is so great that transplanting from a nursery-bed is in most cases to be preferred. The acorns should be sown in November on well-prepared ground, and covered to a depth of 1J or 2 inches; the seeds germinate in the spring, and the seedlings are usually transplanted when one or two years old to nursery-beds, where they are allowed to grow from two to four years, till required for the plantation. Some authorities recommend the tap-roots to be cut in the second year, with the view of increasing the ball of fibre; but, if the trees are removed from the seedbed sufficiently early, the root is best left to its natural development. The oak requires shelter in the early stages of growth; in England the Scotch pine is thought best for this purpose, though Norway spruce answers as well on suitable ground, and larch and other trees are sometimes substituted. The conifers are allowed to grow to a height of from 3 to 5 feet before the young oaks are planted, and are gradually thinned out as the latter increase in size. The distance between the oaks depends upon the growth intended before thinning the young wood; usually they are placed from 8 to 12 feet apart, and the superabundant trees cut out as they begin to interfere with each other. The lower branches often require removal, to ensure the formation of a tall straight trunk, and this operation should be performed before the superfluous shoots get too large, or the timber will be injured; but, as with all trees, unnecessary pruning should be avoided, as every branch removed lessens the vigour of growth. Where artificial copsewood is the object, hazel, hornbeam, and other bushes may be planted between the oaks; but, when large timber is required, the trees are best without undergrowth.
The oak, after the trunk is felled, throws up shoots from the cut stump more surely and abundantly than most trees; hence it is well adapted for the formation of brushwood, of which great quantities are employed in Britain for the manufacture of crates and hoops, and for many other uses. Where the underwood consists mainly of oak it is generally cut once in twenty years, but in some places fifteen years are thought sufficient, while on poor land thirty years are sometimes allowed to intervene between the cuttings. Oak coppices are generally cut in the spring, because the bark is then more readily separated, and large timber trees are very often felled at the same period; but winter felling is probably best when sound heart-wood is the chief thing in view. The growth of the oak is slow, though it varies greatly in different trees; Loudon states that an oak, raised from the acorn in a garden at Sheffield Place, Sussex, became in seventy years 12 feet in circumference; but the increase of the trunk is usually very much slower, and when grown for large timber oak can rarely be profitably felled till the first century of its growth is completed. The tree will continue to form wood for 150 or 200 years before showing any symptoms of decay. As firewood oak holds a high position, though in Germany it is considered inferior to beech for that purpose. It makes excellent charcoal, especially for metallurgic processes; the Sussex iron, formerly regarded as the best produced in Britain, was smelted with oak charcoal from the great woods of the adjacent Weald, until they became so thinned that the precious fuel was no longer obtainable.
An important product of oak woods is the bark that from a remote period has been the chief tanning material of Europe. The most valuable kind is that obtained from young trees of twenty to thirty years’ growth, but the trunks and boughs of timber trees also furnish a large supply; it is separated from the tree most easily when the sap is rising in the spring. It is then carefully dried by the free action of the air, and when dry built into long narrow stacks until needed for use. The value of oak bark depends upon the amount of tannin contained in it, which varies much, depending not only on the growth of the tree but on the care bestowed on the preparation of the bark itself, as it soon ferments and spoils by exposure to wet, while too much sun-heat is injurious. That obtained from the sessile-fruited oak is richer in tannic acid than that yielded by Q. pedunculata, and the bark of trees growing in the open is more valuable than the produce of the dense forest or coppice. The bark of young oak branches has been employed in medicine from the days of Dioscorides, and is occasionally used in modern practice, chiefly as an astringent: in decoction it is given as a gargle for throat affections depending on relaxation, and is administered in dysenteric haemorrhages and some forms of diarrhoea; it was regarded by the practitioners of a former age as useful in consumption, a disease from which tanners are said to be nearly exempt. Poultices made of the crushed or powdered bark have been used with advantage where astringent external applications are indicated; as a tonic it has in modern medicine given place to other remedial agents. The astringent principle is a peculiar kind of tannic acid, called by chemists querci-tannic, which, yielding more stable compounds with gelatine than other forms, gives oak bark its high value to the tanner. According to Neubauer, the bark of young oaks contains from 7 to 10 per cent, of this principle; in old trees the proportion is much less.
The acorns of the oak possess a considerable economic importance as food for swine. In the Saxon period the “mast” seems to have been regarded as the most valuable produce of an oak wood; nor was its use always confined to the support of the herds, for in time of dearth acorns were boiled and eaten by the poor as a substitute for bread both in England and France, as the sweeter produce of Q. Esculus is still employed in southern Europe. Large herds of swine in all the great oak woods of Germany depend for their autumn maintenance on acorns; and in the remaining royal forests of England the inhabitants of the neighbouring villages yet claim their ancient right of “pannage,” turning their hogs into the woods in October and November. Some trees of the sessile-fruited oak bear sweet acorns in Britain, and several varieties were valued by the ancient Italians for their edible fruit. A peculiar kind of sugar called quercite exists in all acorns. A bitter principle to which the name of quercin has been applied by Gerber, its discoverer, has also been detected in the acorn of the common oak; the nutritive portion seems chiefly a form of starch. A spirit has been distilled from acorns in process of germination, when the saccharine principle is most abundant.
The British oak grows well in the northern and middle States of America; and, from the superiority of the wood to that of Q. alba and its more abundant production of acorns, it will probably be much planted as the natural forests are destroyed. The young trees require protection from storms and late frosts even more than in England; the red pine of the north-eastern States, Pinus resinosa, answers well as a nurse, but the pitch pine and other species may be employed. In the southern parts of Australia and in New Zealand the tree seems to flourish as well as in its native home.
The oak in Europe is liable to injury from a great variety of insect enemies: the young wood is attacked by the larvae of the small stag-beetle and several other Coleoptera, and those of the wood-leopard moth, goat moth, and other Lepidoptera feed upon it occasionally; the foliage is devoured by innumerable larvae; indeed, it has been stated that half the plant-eating insects of England prey more or less upon the oak, and in some seasons it is difficult to find a leaf perfectly free from their depredations. The young shoots are chosen by many species of Cynipidae, and their allies as a receptacle for their eggs, giving rise to a variety of gall-like excrescences, from which few oak trees are quite free.
Of the European timber trees of the genus, the next in importance to the British oak is...
