ARBORICULTURE comprises all that relates to the culture of trees, and is one of the great divisions of agriculture; it is a branch of rural economy of much more recent date than either the culture of grain and herbage plants, or the breeding and rearing of cattle. The culture of those plants which supply the food of man or nourish the domestic animals must have exclusively occupied his attention for many ages; whilst the timber employed in houses, ships, and machines, or for fuel, was found in the native woods. Hence, though the culture of fruit-trees, and occasionally of ornamental trees and shrubs, was practised by the Egyptians, Greeks, and Romans, the cultivation of timber-trees on a large scale only took place in modern times. In the days of Charlemagne, the greater part of France and Germany was covered with immense forests; and one of the benefits conferred on France by that prince was the rooting up of portions of these forests throughout the country, and substituting orchards or vineyards. Artificial plantations appear to have been formed in Germany sooner than in any other country, apparently as early as the 15th century. In Britain planting was begun, though sparingly, a century later. After the extensive transfers of property on the seizure of the church lands by Henry VIII., much timber was sold by the new owners, and the quantity thus thrown into the market so lowered its price, as Hollingshed informs us, that the builders of cottages, who had formerly employed willow and other cheap and common woods, now built them of the best oak. The demand for timber constantly increased, and the need of an extended surface of arable land arising at the same time, the natural forests became greatly circumscribed, till at last timber began to be imported, and the proprietors of land to think, first of protecting their native woods, afterwards of enclosing waste ground, and allowing it to become covered with self-sown seedlings, and ultimately of sowing acorns and mast in such enclosures, or of filling them with young plants collected in the woods,—a practice which exists in Sussex and other parts of England even now. Planting, however, was not general in England till the beginning of the 17th century, when the introduction of trees was facilitated by the interchange of plants by means of Botanic Gardens, which, in that century, were first established in different countries. Evelyn’s Sylva, the first edition of which appeared in 1664, rendered an extremely important service to Arboriculture; and there is no doubt that the ornamental plantations, in which England surpasses all other countries, are in some measure the result of his enthusiasm. In consequence of a scarcity of timber for naval purposes, and the increased expense during the war of obtaining supplies from other countries, planting received a great stimulus in Britain in the early part of this century. Since the peace of 1815 the rage for planting with a view to profit has subsided; but there is a growing taste for the introduction of trees and shrubs from foreign countries, and for their cultivation for ornament and use. The profusion of trees and shrubs planted around suburban villas and country mansions, as well as in town squares and public parks, shows how much arboriculture is an object of pleasure to the people. The progress of the Arboricultural Society of Scotland, founded in 1854, and now containing 600 members, is a further indication of the national taste. Again, it may be remarked, that while isolated trees and old hedgerows are disappearing before steam cultivation, the advantages of shelter from well-arranged plantations are more fully appreciated; and more attention is paid to the principles of forest conservancy both at home and abroad. In all thickly peopled countries the forests have long ceased to supply the necessities of the inhabitants by natural reproduction; and it has become needful to form plantations either by Government or by private enterprise, for the growth of timber, and in some cases for climatic amelioration. In British dependencies the Government of India have acted with greatest vigour, having formed a State Forest Department, one object of which is the culture of the most valuable timber trees, as the teak in Malabar, Central Provinces, and Burmah, the Deodar in the Himalayan valleys, and Babool (Acacia arabica), &c., which covers large tracts both in South and North India, for the supply of railway fuel. The successful growth of Australian acacias and gum trees on the Nilgiri hills, mahogany in Bengal, and the spread of the cinchona cultivation on various mountain ranges, testify to the energy and skill with which the culture of exotic trees is carried on in British India. Before giving a sketch of the present practice of arboriculture, it is necessary to premise that this article is confined to well-known and hardy British trees, to a few valuable foreign species, and to plantations made with a view to timber produce.
General View of the Trees cultivated in Britain.— Trees differ from one another in regard to magnitude; slowness or rapidity of growth; suitableness for particular soils, and for elevated exposed situations, or low and sheltered places; texture, colour, and durability of the timber; delicacy or hardiness; ease or difficulty of propagation and rearing; production of showy flowers or fruits; and in other respects. In regard to magnitude, those trees which, in Britain, and in the same parallels of north latitude attain the greatest height, are the spruce and silver fir, the larch, and Scotch pine; and these also are the trees which, in most parts of Britain, produce the greatest quantity of timber in their trunks relatively to that contained in their branches, and in the shortest time. Poplars, willows, and some species of elm, are rapid-growing trees; their timber is rarely contained in one straight trunk, as in the case of pines, a considerable portion being distributed among the branches. Hence, where the speedy production of timber is the main object, pines are the preferable trees for planting. Where landscape effect is more desired than the production of timber, some of the poplars and elms, the Huntingdon willow, in some situations the birch, and in others, such as on the sea-shore, the sycamore and tamarisk, are suitable trees. Where the object is to clothe a sterile surface of dry sand, the birch, Scotch, Austrian, and cluster pines are among the best trees we have; and if the situation be exposed to the sea-breeze, the common and the Norway maple may be substituted; in the warmer parts of the island, the evergreen oak (Quercus Ilex'); and for the marshes of the warmer parts, Taxodium distichum or deciduous cypress. For moist soils which cannot be drained, the white, trembling, and Ontario poplars have the property of sending their roots along the surface of the ground. Some species of willow and some poplars will grow near water in situations where their roots can enter into it, but will not grow in undrained soiL All the known species of trees and shrubs may be successfully grown in almost any kind of soil not beyond average moisture, dryness, or tenacity. In some soils, however, they thrive better than in others, and the timber produced generally varies in quality according to the soil. Thus, a rich soil, while it contributes to the rapid growth of the coniferous tribe, renders their timber less durable; and the same law holds, more or less, with every other species of tree.
The influence of climate on trees is much greater than that of soil; for, whilst many trees grow on any soil, every tree may be said to have its particular climate; that is, a climate in which, the soil and other circumstances being suitable, it will produce the largest and most enduring timber. Hence, when we take the geographical range of any species, we find what may be called a central climate, where it attains its largest size; and as it recedes from this climate, by latitude or elevation, into one either colder or hotter, it gradually diminishes in size, till it at last appears in the form of a shrub. Thus the common oak, which in Britain attains its largest size in Sussex and Hampshire, dwindles into a shrub on the mountains of Scotland and in the north of Africa; its degeneracy being occasioned in the one case by extreme cold, and in the other by extreme heat. Even within Britain the absolute character of trees, relatively to climate, is obvious. The English or narrow-leaved elm, supposed to be a native of Asia Minor and of China, attains a large size near London, producing a great bulk of timber in a short period, and ripening its seeds; while in Scotland it is considered only an ornamental tree. The Lombardy poplar, which in the central counties of England attains 125 feet in height in fifty years, is seldom seen of timber size in Scotland. The sweet chestnut and walnut, cultivated both for fruit and timber in many parts of England, can rarely be grown with profit for either purpose north of Newcastle.
Climate may be considered in regard to the average yearly and monthly temperature, and the degree of atmospheric moisture. A high annual temperature is no proof that a climate is suitable for trees; but a high summer temperature is suitable for many kinds, though the winter temperature may be very low. Thus the oaks and other trees of North America, attaining there a prodigious size, survive a winter as cold as that of St Petersburg, where no native oaks are found; but North America enjoys a very high temperature during summer, which rapidly develops the foliage, and matures the young shoots, enabling them to withstand the most rigorous winter. The much larger rainfall of that portion of America, as compared with St Petersburg, has doubtless important bearings on the question. In England the average temperature of the year is as great as that of the oak countries of the United States; but summers in the former country are comparatively cold, moist, and more cloudy; and though its winters are much milder than those of the latter, the spongy, unripened, young shoots are always more or less injured by frost. Again, in a mild climate, the trees of those countries which have a severe winter come into leaf earlier in the spring than the indigenous trees, and frosts often occurring at that season, they are liable to injury.
Evergreen trees form an important division of the vegetable kingdom; and of these there are two classes, distinct relatively to climate and temperature. The first comprises the conifers, which endure a degree of cold as great as that in which any deciduous tree thrives; and the second, the broad-leaved evergreen trees, such as the holly, box, laurustinus, laurel, evergreen oak, cork-tree, and the evergreen magnolia, trees of comparatively mild climates, and always indigenous on islands or on continents at low elevations, and at no great distance from the sea: hence the large number of evergreen trees which grow well in Britain, compared with those which survive the winter in the same latitude on the Continent.
A small proportion only of the trees cultivated in Britain are indigenous. Some are natives of other parts of Europe, and about two-thirds of the whole are from North America. Of these North American trees there are scarcely any worth cultivating in Britain for their timber, the summer not being sufficiently hot and light to bring the timber to maturity. The most useful trees of Britain are those which are indigenous, such as the oak, ash, broad-leaved elm, Scotch pine, &c.; or those found in the same hemisphere and in the same parallels of latitude, such as the larch, spruce, silver fir, &c. Of all trees cultivated in Europe, the most valued for the strength and durability of its timber is the common oak; and next perhaps to it, the larch. The trunk of the oak, when freed from the soft or outer wood, and thoroughly seasoned by exposure to the air, will last an unknown period of time in buildings and machines. The common European oak is more durable as timber than any of the American oaks, even when grown in America, unless we except the live oak (Quercus virens) ; and no timber equals it for ship-building, except the teak of India. The most generally useful timber grown in Britain is the Scotch fir; but as this is imported from the north of Europe, and a substitute for it from North America, it is not planted in Britain so extensively as it otherwise would be. The timber of the larch is more durable than that of the Scotch fir; but being apt to warp, and not so easily worked, it is less convenient for house-carpentry and joinery. The timber of the common ash is valuable in the construction of agricultural instruments and machines, and it is one of the few woods which are almost as valuable when young as when mature. The wood of the broad-leaved elm is strong and durable, but that of the English and Dutch elms is less so. The wood of the poplar and of the willow, when exposed to constant atmospheric changes, speedily decays; but when thoroughly seasoned, and kept perfectly dry, it is very durable.
Trees suited for Particular Purposes.
1. Conifers or resinous trees; 2. Hard-wood trees ’ and 3. Soft-wood trees.
1. Conifers.
Coniferous trees are characterised by straight erect trunks, with branches in regular tiers, which do not acquire the size of timber. They never send up shoots from the stool when cut over at the ground. The leaves are generally linear or needle-shaped, without veins, and evergreen. The seeds are produced in cones, and the whole plant is more or less resinous. They belong to the Gymnosperms, a family of the Dicotyledons.
The Larch (Larix europoea, D.C.) produces the most valuable timber, which is of great durability. Young larches, 6 or 8 feet high, are useful for sheep stakes, rustic palings, or dead fences. Young trees from 10 to 15 feet in height are found to form excellent hop-poles. 1 The 1 For the durability of the mature timber, both in civil and naval architecture, we may refer to the Transactions of the Highland Society of Scotland, vol. xi. p. 165, and Loudon’s Arboretum Britannicum, vol. iv. p. 2387.
bark of the larch is of considerable value in tanning; and as the leaves are deciduous, grass groλvs better under its shade than under any other species of pine. The larch is readily increased by seeds, which ripen abundantly in Britain; it prospers best in cool argillaceous soil, moist rather than dry, and at a considerable elevation above the sea. In certain soils, it is subject to decay of the heartwood; and of recent years disease has seriously affected many of the finest plantations in this country, especially those beyond the age of fifty years. The larch is indigenous in the alpine region of Central Europe, and is a striking example of the successful introduction of an exotic, having been completely naturalised in Scotland for more than a century. Other species of Larix, natives of Siberia and North America, are inferior as forest trees.
The Scotch Pine (Pinus sylvestris, L.) is, next to the larch, the most valuable coniferous tree grown in Britain. It furnishes the yellow deal of the Baltic and Norway, which is unequalled by any other pine in Europe or North America. The best grown in Britain is produced in the native Highland forests; but there is reason to believe that artificial plantations, in similar soils and situations, would produce timber of nearly equal value. This tree is readily increased from seeds, which, unfortunately, are produced in the greatest abundance on stunted or inferior trees. It is very desirable to select seeds from the best varieties, as is now systematically done by nurserymen. The Highland variety with horizontal branches is that of highest repute. The Sβotch fir is a native of Europe and Asia, but not of America.
The Cluster Pine (Pinus Pinaster, Sol.) is not adapted for general culture in Britain, and therefore scarcely merits to be ranked among British timber-trees. In some parts of the east coast of England, however, plantations of this tree have been raised; and in deep sandy soil it produces a considerable bulk of timber in a short time, thriving better when exposed to the sea-breeze than any other pine. The wood is not so durable as that of the Scotch pine; but it may be employed in the joinery of ordinary apartments. In general, however, it is not sufficiently strong for the roofing, joists, and other carpentry of dwelling-houses. In France, and particularly in the neighbourhood of Bordeaux, it is extensively grown on the sandy wastes, for the production of resin, tar, and pitch, which are obtained by incisions made in the trunk, and by subjecting the wood to the action of fire. The seeds are ripened in England. The young plants require more care in transplanting than those of most other pines, being furnished with a stronger tap-root. The cluster pine is a native of the south of Europe and Algeria.
The Spruce Fir (Abies excelsa, D.C.) is, as a British timber-tree, next in value to the Scotch pine. The young plants and the spray are durable; and the trunk grows straighter, more erect and slender, than the larch. The trunk is seldom sawn into boards; the great value of the tree being for poles of every kind, from those fit for the hop up to masts for smaller ships. It is often used with the bark on, for poles or fence-wood. In most parts of Europe, the poles used in the scaffolding employed in erecting buildings are formed of this tree, the wood being light and elastic. The spruce fir ripens seeds abundantly in Britain, from which plants are as easily raised as the Scotch pine and the larch. It prefers a rather moist soil, and only attains a great height in sheltered situations; but it grows anywhere to a size fit for hop-poles or fencing in a short time. Like the Scotch pine, it is subject to few diseases. The spruce is a native of Germany, Sweden, Russia, and Norway, but not of Britain or of North America.
The Silver Fir (Abies pectinata, D.C.) the largest of the European conifers, in various soils and situations produces a great bulk of timber in a comparatively short period; the timber is considered less strong and durable than that of the spruce fir or the Scotch pine, but it does not warp, and is adapted for all kinds of carpentry. The timber is white, and when not exposed makes excellent flooring. The tree is of slow growth for the first ten or twelve years; nevertheless, even in the north of Scotland it attains the height of 100 feet in sixty or seventy years. It ripens seeds in Britain, but more sparingly than the spruce fir, and plants are easily raised. It is in general healthy, but its cultivation is more difficult than that of the spruce, as the shoots of young trees are liable to be killed by frost. This species is also very subject to the attacks of an insect, Eriosoma, which often causes the death of the tree. The silver fir is a native of Central Germany, and of the mountains of Italy and Spain. Nearly allied is the Abies balsamea, balm of Gilead fir, a native of North America, which produces the Canada balsam, but it cannot be recommended for cultivation, as it is short lived.
Many conifers might be mentioned which, though not producing timber in Britain, are worthy of cultivation. Of the American pines we have the Pinus Strobus, L., Weymouth pine, which furnishes the white wood of American commerce. Several Californian pines have been introduced; of these Abies Douglasii is the most promising. Cupressus Lawsoniana is a beautiful tree, and also Sequoia gigantea, the mammoth tree, a general favourite in pleasuro grounds, but a considerable period must elapse before wo can judge of their being adapted for general culture as timber trees in this country. Of Asiatic conifers, Cedrus Deodara and Libani are much grown for ornament. Pinus excelsa, which resembles the Weymouth pine, and Abies Smithiana and Webbiana grow fairly in many parts of Britain; the Smithian pine being apparently the best adapted to the climate.
The Yew Tree (Taxus baccata, L.) attains its full perfection in this its native country; but on account of its slow growth it cannot be recommended to the planter, whose main object is profit.
Broad-leaved Trees (bois feuillus') in contradistinction to needle-leaved, are classed, according to their timber, in two subdivisions, hard and soft wood trees. They are characterised by large trunks and widely spreading woody branches, and broad leaves with branching veins; they send up shoots from the stool when cut over by the...
