ARBORICULTURE
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 ground; and they are deciduous. They belong to the Dicotyledons.
2. Hard-wood Trees. The hard-wood Timber-trees of Great Britain are characterised by the comparative hardness and durability of their wood, and comprise the oak, ash, elm, beech, sweet chestnut, walnut, and Robinia or false acacia. The British oak includes two sub-species, the stalked fruited or most common oak, Quercus pedunculata, and the stalkless fruited or less common oak, Quercus sessiliflora. The latter grows more erect and more rapidly than the other, particularly if the soil be good. In England and the lowlands of Scotland, Q. pedunculata is the commoner of the two oaks; but in North Wales and the hill parts of northern England, Q. sessiliflora is more frequent. Intermediate forms between these two oaks are found in England and elsewhere, and the leading botanists of the day unite them under the old name of Q. Robur. The wood of the oak is the strongest and most durable of all British timber-trees; but on account of the slowness of its growth it is not always the most eligible for planting. Oak plantations are more valuable than others when in a young state, on account of their bark. From the demand for oak as ship-timber, the price of trees fit for that purpose is always considerable; but the largest trunks employed in naval architecture do not afford an adequate return for tlιe number of years thej have stood on the ground. Accordingly, we find that the Governments both of France and England grow this description of timber largely in national forests. The wood oi the oak is applicable to a greater number of uses than that of most other trees. Houses, ships, furniture, and machines may be formed almost entirely of oak, and consequently there is a ready sale for this timber almost everywhere. Hence there is more inducement to plant it in Britain than any other hard-wood tree. It is easily raised from acorns, which ought to be collected from the most vigorous trees. The British oak is a native of most parts of Europe, but not of Asia, Africa, or America.
The Ash (Fraxinus excelsior, L.) is in Britain next in value to the oak as a timber-tree. It requires a good deep loam with gravelly subsoil, and a situation naturally sheltered, such as the steep banks of glens, rivers, or lakes; in cold and wet clay it does not succeed. As the value of the timber depends chiefly on its toughness and elasticity, it is best grown in masses where the soil is good; the trunk is thus drawn up free from large side-branches. The tree is a native of Central Europe, and is easily propagated from seeds. It throws up strong root shoots. The ash requires much light, but grows rapidly, and its terminal shoots pierce easily through thickets of beech, -with which it is often associated. Unmixed ash plantations are seldom satisfactory, because the foliage does not sufficiently cover the ground; but when mixed with beech it grows well, and attains great height and girth. Coppice shoots yield excellent hop-poles, crates, hoops, whip-handles, &c. The timber is much used for agricultural implements, and by coach-builders and wheelwrights. The supply of this valuable timber is annually becoming more limited on account of the decreasing use of hedgerow trees.
Of the Elm there are two species, the common or narrowleaved elm (Ulmus campestris, L.), and the Wych or broadleaved elm (Ulmus montana, L.) There are many varieties, such as the Dutch elm and the smooth-leaved or Huntingdon elm, the latter much valued for its timber. The narrowleaved elm is not very common in Scotland, but in the central districts of England it becomes a handsome tree; and the timber is used for important purposes in shipbuilding, as well as in the construction of machines and agricultural buildings. The Wych elm is a hardy tree, of rapid growth; but, unless planted in masses, it seldom produces a straight handsome trunk. It strikes from layers with great facility, and when a branch touches the ground it is sure to take root. Few trees are more difficult to uproot than Ulmus montana, and it is rare to see it thrown over by the wind. It has a wide-spreading head, often sloping to one side, and lashing its neighbours with such force that it is sometimes interdicted in mixed plantations. Its timber is more durable than that of the English elm, or of any of the hybrids. It is much used in agricultural carpentry, in rural machinery, and in household furniture. The Wych elm produces abundance of seeds, which, if sown as soon as they are gathered, often come up the same year; but the English elm and the hybrids produce seeds sparingly, and are usually propagated by layers or by grafting on the Wych elm. One remarkable difference between the English and Wych elms may be noticed, viz., that the latter never throws up suckers from its roots; and it is therefore peculiarly valuable as a stock for the English elm, and for those varieties which do throw up suckers. There are other species and varieties of European elms, and several kinds of American elms, but none are deserving of culture in Britain as timber-trees. The elm is subject to the ravages of several insects, especially Scolytus destructor.
The Beech (Fagus sylvatica, L.) is one of the largest British trees, particularly on chalky or sandy soils. It is a handsome tree in every stage of its growth, but is more injurious to plants under its drip than other trees, so that shadebearing trees, as holly, yew, and thuja, suffer. Its leaves, however, enrich the soil. In England and America the beech has a remarkable power of holding the ground where the soil is congenial, and the deep shade prevents the growth of other trees. It is often and most usefully mixed with oak and Scotch fir. The timber is not remarkable either for strength or durability. It was formerly much used in mill-work and turnery; but its principal use at present is in the manufacture of chairs, bedsteads, and a variety of minor articles. It is a native of the south of England, and of various parte of the continent of Europe. There are some varieties, particularly the purple and weeping beech; and there are one or two species natives of North America, but none of them deserve notice as timbertrees. It is propagated by its mast, which is produced plentifully in fine seasons.
The Hornbeam (Carpinus Betulus, L.) is an indigenous, moderate-sized, slow-growing tree, bearing a general resemblance to the beech, though of less value. It coppices well, and along with beech is valued for making hedges, as these trees retain their leaves a great part of the winter. The hornbeam is propagated by its nuts, which are produced in abundance. The wood is used for tool-handles, cogwheels, and screws. Selby (British Forest Trees') recommends the use of the hornbeam as a nurse-tree.
The Sweet Chestnut (Castaneaυulgaris, Lam.) is a large, long-lived, deciduous tree, of rapid growth while young, and attaining a vast size in South Europe (e.g., the renowned chestnut of Mount Etna). It was early introduced to England, and is one of its most ornamental trees. The timber bears a striking resemblance to that of the oak, which has been mistaken for chestnut; but it may be distinguished by the numerous fine medullary rays. Unlike oak, the wood is more valuable while young than old. When not more than fifty years old it forms durable posts for fences and gates; but at that age it often begins to deteriorate, having ring-shakes and central hollows. In a young state, when the stems are not above 2 inches in diameter at the ground, the chestnut is found to make durable hoops for casks and props for vines; and of a larger size it makes good hop-poles. It is a native of Asia, North Africa, and North America. In Spain and Italy it is grown for its fruit, in Britain, for ornament. In the south of England in warm seasons it ripens its fruit, from which plants are easily raised. None of the other Continental or American species are cultivated in Britain for their timber.
The Common Sycamore or false plane (Acer Pseudo-Platanus, L.), the plane-tree of Scotland, is a large tree naturalised in Britain, though seldom attaining the height of those already mentioned. It withstands the sea and mountain breezes better than most other timber trees, and is often planted near farm-houses and cottages in exposed localities for the sake of its dense foliage. Its wood is valued in turnery, for cups, bowls, and pattern blocks. It produces abundance of seeds, and is easily raised, but it requires good and tolerably dry soil; it will not thrive on stiff clays nor on dry sands or chalks. The Norway maple (A. platanoides, L.) is a hardy tree, used as a breakwind in exposed situations on the east coast; but neither it nor the other species from Europe or America seems to deserve cultivation for the sake of its timber. The sugar maple (A. saccharinum, L.) forms extensive forests in North America. It has been introduced into Britain for a century, but is rather tender, and requires a dry sheltered situation. It is propagated by imported seeds, and it is doubtful if it can be profitably cultivated in this country.
The Common Birch (Betula alba, L.) is a tree of the second rank, worthy of culture in inferior soils and situations, especially as coppice-wood. The spray, in some parts of the country, is sold to the besom-maker, and gives a fair return. The tree seeds freely, and is easy of management. It is often planted in poor soil as a nurse for oak and sweet chestnut. It yields excellent fuel. The wood is used for carving, furniture, and agricultural implements, and in the Highlands of Scotland and Sweden for building material. The bark, covered with a layer of earth, is used in roofing, and baskets and boxes are made of it. The weeping birch forms one of the most beautiful features in Highland scenery. None of the American or Himalayan birches have yet been planted with a view to profit as timber-trees, though cultivated for many years.
The Common Walnut (Juglans regia, L.), is mentioned in the earliest British botanical writings, and is supposed to have been introduced by the Romans. It grows well, and ripens its fruit in the southern and midland counties of England; but large trees may be seen as far north as Boss-shire in sheltered places. The fruit is in some years plentiful, but ripens only in the hottest summers. The timber is excellent, and held the first place for the manufacture of furniture till the introduction of mahogany, and on this account the tree merits more attention. It is raised from the nuts, like horse chestnuts; the seedlings should be protected from frost during the first winter. The rate of growth is not rapid, and a deep soil is essential to success. If cultivated for the fruit, the seedlings should be transplanted once or twice.
The Robinia or false acacia (Robinia Pseud-Acacia, L.) is a tree of unquestionable beauty, and much has been written of the value of its timber. It was introduced from North America in the 17th century, and has been extensively cultivated as an ornamental tree. In 1825 Cobbett strongly recommended the planting of it for its timber. It has been used largely in England for hop-poles, and in France for vine-props. In America it is much used for trenails or wooden pins for bolting ship timbers. It is now planted sparingly, the English summer not being sufficiently long and warm to ripen the shoots. The tree is readily produced from imported seeds, and occasionally from suckers, which are abundant. It should be planted in sheltered situations in dry friable loam. It grows rapidly the first few years, but the trunk in Britain rarely exceeds 1 foot in diameter.
Amongst hard-wooded trees of the third rank, the timber of which is useful, are Cerasus sylvestris, the wild cherry or gean; Cratoegus Oxyacantha, whitethorn; Pyrus aucu-paria, mountain ash or rowan; P. Aria, white beam tree; P. Malus, crab-tree; P. communis, wild pear; Ilex Aquifolium, holly; and Cytisus Laburnum, laburnum. A plantation formed solely of any of these trees is not to be recommended, but when ,they are self-sown or introduced by way of variety or ornament, it is well to know that their timber is of some value; the laburnum, yew, and holly are the most valuable of the trees of the third rank.
3. Soft-wood Trees.
The soft-wood trees are remarkable for the rapidity of their growth, the lightness and whiteness of the wood, and often for their early decay. Among those worthy of cultivation in Britain for timber, are the poplar, willow, alder, lime, and horse chestnut; the two first being those that are generally recommended with a view to profit.
Of the Poplar (Populus, L.) there are numerous species, and several deserve culture for their timber in situations where the soil is good and deep, and where the roots can reach running water; but they do not thrive in stagnant marshes. The following are the best adapted to our climate :— P. alba, abele or white poplar, is widely distributed over Europe, and is extensively cultivated in Britain. P. canescens, the grey poplar, is classed by Hooker as a sub-species. These trees attain a large size, giving long clean, straight timber, which induces planters to grow it, especially near factories, where the wood is used for flooring, machinery, &c., as it does not easily ignite. The timber is soft, white, and light. The root throws up strong suckers, which always replace trees cut down. P. tremula, the aspen, produces a white wood, which is much sought after for the' manufacture of paper, and on that account it is rising in value. P. nigra, the black or Lombardy poplar, is much planted on the Continent in hedgerows, and also in Kashmir—where the pyramidal variety is common. The wood, which is white, soft, and light, is used for sabots, but is not good for fuel. The bark is used by the tanner. The black Italian poplar (P. monilifera) is always propagated by cuttings of the young wood. It pollards well, and is a rapid grower. Poplars should not have large branches pruned off, and they do not coppice well, because moisture enters cracks in their wood.
The Willow (Salix, L.) is an extensive genus, found in Europe, Asia, and North America, including all the shrubby osier species used for basket-work, as well as a few trees. The arborescent willows are most useful trees, and well merit the attention of planters. They are invaluable for fixing the banks of rivers and canals, and are successfully used for that purpose. As coppice woods with short rotation, they are grown in osier beds, and cut annually for basketwork, or when three or four years old, for hoops, <fcc., and in this way they yield a good return. The laying down and treatment of osier beds may be seen in great perfection on the banks of the Thames. The wood is used for carving and other purposes. In North America, fishing nets and lines are made of the inner bark. All the species are easily propagated by cuttings, and require to be grown in damp soil. There are three species attaining the size of trees— S. alba, the white or Huntingdon willow, reaches a larger size in twenty or thirty years than any other British tree except Populus alba, and often yields 1 foot of solid timber for every year of growth. S. caprea, the goat willow or sallow, occurs generally as a large shrub, but attains 40 or 50 feet in height. It forms a good protection in maritime situations, but often by its exuberant growth injures more valuable trees. The third tree is Ä fragilis, the crack willow, and its sub-species S. Russelliana, the Bedford willow. Another tree willow, S. babylonica, or weeping willow, a native of Russia and China, is very ornamental on islands and river banks. The larvae of several nocturnal Lepidoptera feed upon the leaves of the willows, and the trunk of the sallow is often injured by the perforations of the Trochilium crabroniforme (Lunar Hornet Sphinx).
The Alder (Alnus glutinosa, D.C.) is an indigenous tree met with commonly on the banks of streams, but of smaller size than the poplars and tree willows; it often, however, attains to 40 or 50 feet. It is readily propagated by seeds, but throws up root suckers abundantly. The alder is important as coppice-wood on marshy ground. The wood is soft, white when first cut, and turning to pale red; the knots are beautifully mottled. It is adapted for piles in embankments and bridges; and charcoal of alderwood is valued in the manufacture of gunpowder.
The Lime Tree (Tilia europoea, L.), is a beautiful leafy tree with wing-like bracts, much prized for ornament, and suitable for avenues. It is much planted along streets and promenades, affording a pleasant shade during summer; the blossoms are fragrant, and yield most delicate honey. The lime is generally propagated by layers. Its wood, which is very light and soft, is used by saddlers, shoemakers, glovers, and toy-makers; and for carving and modelling purposes, it is superior to all other British trees. Several American lime trees have been introduced, and appear well deserving of a place in our arboricultural collections.
Tho Common Horse Chestnut (Aesculus Hippocastanum, L.), cultivated in Europe since the 16th century, is an ornamental tree of quick growth in good soil. Its handsome blossom surpasses that of all other British trees, and its massive foliage is effective, but the timber is of an inferior quality, only used for boarding and packing-cases, linings of carts, and wheel-barrows. It is rarely planted in mixed plantations where profit is an object; it interferes with its neighbours, and occupies too much room. It is generally introduced near mansion-houses for ornament and shade, and the celebrated avenues at Richmond and Bushy Park are at the time of flowering objects of great beauty. From the crop of nuts which ripen in October seedlings are easily raised, and should be placed in rich loam, and transplanted before being finally planted out.
Roadside Trees and Hedges.
Little attention is paid to the planting of trees along roadsides, and in such situations healthy or well-shaped ones are seldom seen. A pit should be made of sufficient size (2 to 3 feet square), and filled with good soil mixed with rotten dung. The plante require to be fenced, and for the first summer occasionally watered, and the earth dug and kept clear of weeds. In forming avenues on boulevards, tho trees should be planted 30 feet apart, and if space allows of it, there should be a double row to form a shady arch for pedestrians. The oversight of these is sometimes given to the surfaceman, or to a man appointed for the purpose, and it should be his duty to maintain the avenues complete. Trees, especially in or near large towns, are subject to injuries which disfigure their appearance or retard their growth, and not unfrequently destroy the plants. To prevent this it is customary to surround the stem with a cradle, or matting, or thorny branches.
Hedge-plants are of great importance both for shelter and protection of plantations. By far the best for outside hedges are the common hawthorn and the wild crab. The sloe or black thorn makes an excellent hedge; but it throws up many suckers, and requires constant attention to keep it within bounds. It forms, however, an excellent barrier for picturesque plantations, where it is allowed to spread itself in every direction. Holly and yew hedges are suitable for inner enclosures. The holly forms an excellent hedge, both for gardens and fields, as its leaves are rarely injured by insects; and, being an evergreen, it harbours neither weeds nor vermin at its roots. Birds are also much less apt to build in it than in deciduous hedges. It has two disadvantages, viz., the slowness of its growth, and imperviousness to wind in the winter season. Were holly hedges occasionally introduced among those of the common thorn, they would add greatly to the beauty of the country in winter. The common furze sown on the top of a bank forms an effective hedge in a short period, but it is not durable. In moist soils, willows or poplars, and in situations exposed to the sea-breeze the elder, may be planted; but such hedges can be hardly considered as fences from want of compactness and density of foliage. The land for hedges should be carefully prepared and freed from weeds before planting, and the expense of doing this will be well repaid by the growth of the hedge afterwards. The ground should be cleared of weeds two or three times a year until the plants have reached some height. Hedge plants should not be pruned till after three years, or they will become stunted; after that pruning should take place once a. year. A hedge one-third beech and two-thirds hawthorn is excellent for high and cold situations.
Coppice.
Coppice or Copse consists of self-sown or planted trees periodically cut before they attain the size of timber.
This system of wood cropping was more extensively adopted thirty years ago than it is now, as the value of oak bark is much reduced owing to the introduction of foreign bark and other substances for tanning. One requisite for copse woods is that they should spring up freely from the cut root. Most of the broad-leaved trees and shrubs may be cultivated as coppice wood; in soft, wet soils, birch, alder, and various willows are amongst the most useful trees, and in drier soils the oak, chestnut, and ash are valuable for this mode of cultivation.
ORNAMENTAL TREES AND Sl·lRUBS.
As already observed, we exclude from consideration in this article flowering and fruit-bearing trees and shrubs. We also exclude all those that require special protection, and confine ourselves to trees and shrubs considered ornamental from their general form, and suited for introduction into plantations in most parts of Britain. These are arranged under the heads of evergreen and deciduous.
Evergreen Ornamental Trees and Shrubs.— The climate of Britain enables us to cultivate many evergreens; new species are imported, and varieties are produced by accident or experiment, so that the number is always increasing. All the pine tribe may be described as highly ornamental, and many of them endure the open air in the coldest parts of Britain. The Deodar (Cedrus Deodara) naturally grows in compact forests, clearing itself of side branches like the larch; in this country single specimens have been extensively planted of late years for ornament. Large quantities of seeds are annually imported from the Himalaya, and it is also raised from cuttings. The Lebanon and Atlas cedars (Cedrus Libani and atlantica) are closely allied to the Deodar; and it is proved by Hooker that they cannot be separated by constant specific characters. The Atlas cedar is distinguished by a stiff erect leader, and the foliage is generally dark, that of the Deodar being light or bluish green. Cryptomeria japonica, the Japan cedar, is a beautiful evergreen tree, attaining 100 feet in height, with a pyramidal head; it yields cones abundantly. Sequoia gigantea, the Wellingtonia or mammoth tree, remarkable as the loftiest tree known, attains 300 to 330 feet in height, and 80 to 100 feet in girth, and is a handsome and symmetrical tree. & sempervirens, the redwood of California, is another giant tree, though of smaller size. Both species are hardy in England, and are easily raised from cuttings. The Weymouth pine (Pinus Str obus) is a hardy ornamental tree, introduced in 1705, suited for cold situations; and still more so is the Pinus Cembra, which is of slow and erect growth and long retains the beauty of youth. Pinus excelsa is a hardy and ornamental species, from the Himalaya; but when exposed to wind it does not thrive. It is inclined to seed rather too early and freely in this country. Some of the Californian and British Columbian pines are hardy and ornamental, particularly P. ponderosa, the heavy wooded pine; but it is easily blown over by the wind. Other species are P. Sabiniana, inops, and Nλιrrayana. The Douglas fir (Abies Douglasii, Lindl.) is a handsome tree, as hardy as the common spruce, differing in the dark green colour, and apparently intermediate between the common spruce and the silver fir. It was introduced in 1827, and is of very rapid growth in England and Scotland. At Dropmore there is a tree which, at the age of 44 years, was 100 ft. high, with 9 ft. 7 in. girth at 3 feet above the ground. Many specimens in Perthshire raised from layers and cuttings since 1846, are 50 to 70 feet high. The Mack and white spruces (Abies nigra and alba) of North America are well-known ornaments in our pleasure grounds; and there are some Californian species, such as Abies Menziesii, nobilis, and others, which are hardy, and promise to be valuable additions to our ornamental trees. The Hemlock spruce of Canada (Abies canadensis) is hardy throughout North Europe. The Cephalonian fir (Abies cephalonica, Loudon), closely allied to and probably only a variety of the silver fir, is a handsome tree, readily propagated by cuttings and from cones imported from the Mediterranean. A. Nordmanniana, Link, a stately tree with dark, compact foliage, and ovoid cones, of late years much cultivated in England, forming forests in the Crimea and the Caucasus, is regarded as a variety of the silver fir by Pariatore and Grisebach. A. Pinsapo, Boissier, is a beautiful tree with rigid whorled branches, introduced from Malaga and Algeria; it is much cultivated in England, and thrives well. Abies Smithiana, the Himalayan spruce, closely resembles the common spruce, and is hardy in England and Scotland, where it grows with great vigour; it is readily propagated by cuttings, and by grafting, and British trees already produce cones. Abies Webbiana, Lindl., the Himalayan silver fir, suffers in spring in North Europe, because it starts into growth too early: it is grown in Ireland and the south-west of England. The Chili pine (Araucaria imbricata), a noble tree in its native country, and a conspicuous object in a park from the peculiarity of its whorls of rigid branches, is hardy in many situations in Scotland as far north as Dunrobin. Cupressus Lawsoniana, introduced in 1854 from California, is hardy, and rapidly becomes a handsome tree, ripening its cones. The common cypress (Cupressus sempervirens, L.) grows vigorously in the central districts of England, but scarcely thrives in the northern counties. Cupressus glauca or lusitanica, L., is a beautiful evergreen, with glaucous foliage, but tender; nevertheless, in Ireland it attains a great size. The Ginkgo or maidenhair tree (Salisburia adiantifolia, Sm.) is remarkable for the singularity of its foliage; it is a native of China, but is hardy in many parts of England. Biota orientalis, Endl. (syn. Thuja orientalis, Linn., the Arbor vitce), is a small evergreen tree, indigenous in Japan and China, much cultivated in Europe, with foliage similar to that of the Cypress. The red cedar (Juniperus virginiana, L.), the Phoenician, and other species of juniper, are hardy and ornamental. The holly, boxwood, evergreen oak, and Portugal laurel are universally known and admired, and their glossy foliage makes them specially beautiful in winter.
Deciduous Ornamental Trees.— We can name only a few of the most prominent deciduous trees planted solely for ornament. Magnolia grandiflora is grown chiefly on walls, as it suffers from wind. Its flowers and foliage are very beautiful. The tulip tree (Liriodendron tulipifera, L.) forms a tree of the first rank in the climate of London, and attains a large size in the milder parts of Scotland; for the beauty of its foliage and flowers, it deserves a place in every collection. Pavia indica, the Himalayan horse chestnut, is smaller than the common horse chestnut, but extremely beautiful from its large panicles of variegated blossoms. There is a fine specimen in the Edinburgh Botanic Garden. Koelreuteria paniculata, a native of China, is a hardy tree, very ornamental from its foliage as well as its flowers. There are fine specimens both in England and Ireland, yet the tree is not generally met with in pleasure-grounds. The ailanto (Ailanthus glandulosa), a Chinese plant, is hardy in England. It forms a stately tree with a straight trunk and magnificent foliage, the leaves being sometimes 3 feet in length. In some parts of France it is planted as a timber-tree, and thrives well on chalky soils. The bladder-nut tree (Staphylea, L.) maybe trained to be a handsome low tree, ornamental from its foliage, white flowers, and curious bladder-like capsules. There are two species—N. trifolia and S. pinnata. The common spindle tree (Euonymus europoeus) and the broad-leaved spindle tree (E. latifolius), when trained up to single trees on a deep loamy soil, with ample space, form in autumn, when their capsules are ripe, remarkable and striking objects. The winter-berry (Prinos glaber) is a deciduous shrub, a native of North America, which, like the holly, produces fine scarlet berries, and retains them through the winter. There are several species, all hardy, and worthy of a place in our collections. Sophora japonica forms a splendid tree in the climate of London, and a pendulous-branched variety is very ornamental. In dry and warm seasons, when the leaves of most other trees become of a paler green than usual, those of this tree assume a darker hue. Virgilia lutea is a North American tree, with fine large foliage, hardy in most parts of Britain; and, in America, valued for the yellow colour of its wood. The laburnum has already been mentioned as a useful and ornamental tree. The genus Crataegus consists of many species and a vast number of varieties, among which are many beautiful small trees, remarkable for an irregular picturesque outline even at an early age. They flower and fruit profusely; the flowers are generally white and fragrant, but some varieties are tinged with red and purple; they appear from March to July, and the Glastonbury thorn blooms at Christmas. Cotoneaster frigida, bacillaris, acuminata, microphylla, and nummularia are small trees of great beauty, both on account of their foliage and their fruit. They are from the Himalaya, and hardy in England. They are cultivated in a variety of forms, some of which have been described as distinct species. The wood is hard and elastic. There are many ornamental species and varieties of the genus Pyrus, which now includes species formerly grouped under Sorbus, Mespilus, &c. From the Himalaya we have (P. variolosa), a remarkable tree,· with leaves sometimes like those of the common pear, and at other times lobed or pinnatifid. P. Aria, the white-beam tree, and all its varieties, deserve culture, as compact small trees, remarkable for their large woolly foliage, which dies off a fine yellow, their white blossoms, and showy red fruit. The service tree (Pyrus Sorbus) and its varieties are very ornamental. Pyrus japonica, L., is well known as one of the most ornamental spring-flowering plants in cultivation. Hamamelis virginica, the Wych hazel, is valuable from its beginning to flower in November, and retaining its blossoms till February or March: though rarely seen in collections, it is hardy, and forms a handsome small tree. The snow-drop tree (Halesia tetraptera) is one of the hardiest of North American trees, and, when in flower, one of the most beautiful: it ripens abundance of seeds in this country, by which it is readily propagated; in some parts of England it is, like the American bird-cherry, naturalised in the copses. It is rarely met with in Scotland, though few ornamental trees are so well adapted for the climate. The date-plum (Diospyros Lotus) though it ripens fruit as a standard near London, is tender in the northern counties. The Virginian snow-flower or fringe tree (Chion-antlιus virginica) is nearly as hardy as the snow-drop' tree; and when planted in a moist soil and trained to a single stem, its head is ornamental from its large deep-green foliage, independently of the fine, white, fringe-like flowers, which are suspended from the axils of the leaves. The common purple and white lilacs (Syringa vulgaris and Ä vulgaris alba) are hardy, and make neat small trees when trained to a single stem. The weeping-ash (Fraxinus excelsior, var. pendula) is well known. It suffers much from cattle or sheep browsing on the pendulous branches, disfiguring the plant, which should always be enclosed.
The flowering or manna ash (Fraxinus Ornus), a native of the mountains of South Italy, is a handsome tree, deserving a place in ornamental plantations. It has a fine effect standing singly on a lawn. The medicinal manna it yields is obtained by making incisions in the stem. Catalpa syringoefolia is a splendid tree when in flower: it attains the height of 30 or 40 feet, and sometimes ripens its seeds in the climate of London; but in the northern counties it seldom does much good. It bears a very severe cold in winter, provided there has been heat and sunshine enough in summer to ripen its wood. Of the genus Quercus, 281 species, European, American, and Asiatic, are described in De Candolle’s Prodromus, and a great variety are procurable in British nurseries. The best known European species are Q. Suber, the cork oak; Q. Cerris, the Turkey or mossy cupped oak; Q. Aegilops, the Vallonea oak; and Q. lusitanica infectoria, the gall or dyer’s oak. The Lucombe and Fulham oaks are believed to be hybrids between Q. Cerris and Suber. Q. Ilex, the evergreen or holm oak, a native of South Europe, Persia, and the North-West Himalaya, but introduced into Britain in 1581, and commonly planted, attains a large size, and frequently ripens its acorns. The oaks of· North America are very numerous and interesting, but they do not ripen their shoots sufficiently to be frost-proof. None of the deciduous Himalayan species have yet been successfully introduced.
Propagation and Culture in the Nursery. Nursery Culture. —A nursery is a plot of ground devoted to the propagation and rearing of trees; it should as far as possible be exempt from the influence of frost, which prevails in low situations, and it ought to contain a variety of soils. As a general principle, all seeds will germinate in any soil provided it contains vegetable matter, and is friable, free of stones, and well drained, with a convenient supply of water. If a nursery therefore contains the three leading soils, sand, loam, and peat, it will suffice for all required purposes. With regard to climate, all deficiencies which occur in Britain may be met by glazed frames for raising the more tender kinds. It is the interest of the nurseryman to have his nursery in a fine climate, and in deep fertile soil, that he may raise large vigorous plants in the shortest period; but it is the interest of the purchaser to have the plants reared in a climate and soil inferior to that into which they are to be transplanted, because, when this is done, instead of the plants receiving a check, as is usually the case, they will be improved by transplanting. The strength of a plant and its suitableness for successful transplanting consists in all its parts being developed, in the thorough ripening of its wood, and in the dormant state of its fibrous roots. If by any mode of culture these requisites can be obtained, together with the long and thick shoots which are produced by growing the plants in deep rich soil, so much the better; but in the climate of Britain trees reared in nurseries with inferior and unmanured soil are likely to prove most hardy. Those who plant in mountainous districts will always find it better to have their nurseries on the sides of mountains than in the valleys.
Propagation.— Trees are chiefly propagated by seeds, but also by cuttings, layers, budding, and grafting. The timber-trees of all countries are raised from seeds, with a few exceptions, such as the poplar and willow, which are raised from cuttings, and some species of elm, lime, and a few others, which are raised from layers or by grafting. Most ornamental trees are raised by some of these artificial methods, because in this country they seldom ripen seeds. Thus, all the American oaks may be grafted on the common British oak. Most of the foreign maples and birches are raised by layers, most cf the ornamental thorns by budding and grafting, and willows and poplars by cuttings. AU plants which do not ripen seeds readily are propagated artificially, and that mode is preferred by the nurseryman, which experience has proved wi∏ produce the largest and most vigorous plants in the shortest time. Thus, though more suitable plants would be produced by raising the plane and poplar from cuttings, because in that case nature would adjust the tops to the power of the roots, yet as much ’.larger plants are produced by layers, that mode is preferred in commercial nurseries. The lime tree and English elm ripen their seeds in Britain, but large plants are much more rapidly procured in the first case by layers, and in the second by grafting: the mode by which the largest plants are most rapidly produced need not always give way to the slower method; but in most cases, it would be advantageous to the purchaser that the slower mode should be adopted. According to some writers, seedling plants are of greater durability than those raised in any other way; but though this may be true in some cases it is not universally applicable, as we know that a bud produces as perfect a plant as a seed; the only difference being that the bud seems more fully imbued wtth the peculiarities of the individual which produced it than the seed. The poplar, willow, vine, <fcc., have been propagated by cuttings from time immemorial, and appear to possess respectively the same properties now that they did in the days of the Romans. Seeds should be collected when mature from the best specimens; and should either ba sown immediately, or preserved in a place where they will, undergo few atmospheric changes till the proper sowing season, which in most cases will be the following spring. Nature, it may be observed, sows all her seeds soon after they are matured; that is, they drop from the tree upon the ground in autumn or the beginning of winter, or, in the case of some trees, such as the conifers, not till spring; but when seeds are thus left to sow themselves many are destroyed by animals, many fall in unfavourable positions for germination, and only a small proportion produce plants. It is for the arboriculturist to study nature’s mode of sowing, and to imitate only her favourable features. The greater number of seeds may be stored till the following spring, that is, till February or March, and then be committed to the soil. Poplar and willow seeds, however, ripen early, and when sown immediately on dropping from the tree, often come up in the course of a few weeks; whereas, if they are kept till spring, the greater number dα not come up at all; and seeds which lie two years in tha ground before coming up, such as those of the hawthorn, the holly, <fcc., may be kept till the second spring before they are sown.
In order to show the treatment required for different kinds of seeds, and the plants raised from them, it will be convenient to throw them into the following groups :— Trees producing (1) cones; (2) nuts, acorns, masts, or keys; (3) cottony or feathery seeds; (4) fleshy fruits; or (5) leguminous seeds.
Coniferous Trees.— Coniferous trees ripen their seeds from October till January, and if the cones remain on the tree throughout the winter the seeds do not generally drop out till April or May; such as drop into favourable soil come up in five or six weeks. The cones should be collected immediately after they are ripe, and laid in a dry place. The seeds are extracted by exposing the cones to the heat of the sun under glass, or by subjecting them to artificial heat before an open fire, or on a kiln. The seeds are sown in April, in soil dug over and finely raked; and then covered with a thin coating of soil. The beds, after the sowing is completed, should be shaded from the sun by branches of tree. In cold moist climates, such an that of Aberdeen, this shading may be dispensed with: but in the climate of London it is in most seasons necessary, and may be effected by mats, straw, or evergreens. For convenience, the seeds are generally sown in beds, a slight excavation being made by drawing some of the earth to the sides; and in order that the seeds may be evenly deposited on a somewhat firm surface, the bottom of this excavation is lightly rolled. After the seeds are scattered over the beds they are again rolled, and the covering of earth thrown over them. It is found that the rolling of the beds before and after sowing, by bringing the seeds into close contact with the soil, accelerates germination. The more tender pines are sown in pots or flat earthen pans, for the convenience of making them germinate under glass, and to facilitate future transplantation; but the process of sowing is exactly the same. The seedlings require nothing but the usual culture of the nursery for two summers; after which they should be transplanted where they are finally to remain; or they should be planted in the nursery in lines, or scattered over beds; in either case they should be 3 to 6 inches apart, according to their height and the length of the leaves. For the Scotch pine and spruce fir, which grow slowly when young, 3 inches are sufficient; for'the larch, which grows rapidly, and for the pinaster, which has long leaves, 6 inches are required. Here the plants may remain two years, and afterwards be again transplanted; unless they are in the meantime removed to where they are to remain, which, to ensure good timber trees, should be done before young conifers exceed four years’ growth.
Trees bearing Nuts, Acorns, Masts, Keys, &c.— These ripen from October to December. Acorns usually in November; but the beech, horse chestnut, walnut, and hazel, ripen their fruit in October, and most of the sycamores and maples in September. All these ought to be gathered as soon as ripe, because the best are liable to be picked up by wild animals as soon as they drop. They may be sown immediately or kept till February, as in neither case will they come up till April or May. The seeds should be sown in a sandy loam, in drills, at such a distance from each other that the leaves of the seedlings may not touch at the end af the first season; they should be gently pressed down into the soil, and covered to twice the depth of the seed. Drills are recommended for this description of tree-seeds that a spade may be inserted obliquely between the rows, so as to cut the tap-root of the plants, and force it to throw out lateral roots. This is commonly done in the spring of the second year, and, by increasing the lateral roots and their fibres, renders the tree better adapted for transplanting. At the end of the second year plants so treated may be taken up, and either planted where they are to remain, or transplanted into nursery lines, at distances suited to the habit of the species. Here they may remain two years longer, and be again replanted. The larger and stronger broad-leaved tap-rooted trees are, up to a certain point, before they are removed from the nursery, the more vigorously will they grow where they are finally to remain. The size to be attained in the nursery must depend on the condition of the soil into which they are to be transplanted. If moisture be so abundant as to supply the fibrils with water during the first summer, even if the removed plant has a stem an inch in diameter, so much the better; it being understood that it has been transplanted in the nursery every two years, and is therefore well supplied with fibrous roots, and. has its wood perfectly ripe. If, on the other hand, the soil into which the plant is to be transplanted is dry and poor, the plants should be removed there at the end of the second year, because such plants, being of small size, have few leaves to exhale moisture, and before they grow large they will have adjusted their roots and annual growths to the locality.
Trees with Cottony, Feathery, and other soft Seeds.— The seeds of the genera Populus, Salix, Alnus, Betula, Ulmus, &c., ripen from May to November; poplars in May; willows and elms in June; alders in November; and birches in October. The seeds of the alder and birch may be kept in a cool, dry, airy situation till spring, or sown immediately after they are gathered. They come up in the May or June following; but the seeds of the elm, poplar, and willow should be sown immediately. Many will come up the same autumn, and the remainder the following April and May. The seeds may be dried and preserved in bags for a year; but in this case the greater part will not vegetate. Poplar and willow seeds require to be sown on a surface rendered level and slightly firm by rolling. After the seeds are equally distributed over it, they should be covered with light sandy soil, or vegetable mould, no thicker than barely to conceal the seed. After this the bed should be watered and shaded and kept uniformly moist by occasional watering when the plants make their appearance. Of all seedling trees raised in British nurseries, none grow with so much vigour the first year as the common elm; and, therefore, the seeds of this tree require to be placed at a greater distance from each other than those of any other kind. The seeds of the elm keep better till the following spring than those of the poplar and willow.
Trees with Fleshy Fruits.— The fruit of the genera Pyrus, Cotoneaster, Viburnum, Cratoegus, Ilex, Prunus, Cerasus, Rhamnus, &c., ripens from August to December. It should be gathered when ripe, mixed with sand, and laid in a heap till the pulp rots away. With some species the seed may be sifted from the sand and sown in the following February, the seedlings being treated as the seedlings of the conifers. In others the heap may be left for two years, and many of the seeds will not germinate till the third spring.
Trees with Leguminous Seeds.— These include the genera Cytisus, Acacia, Robinia, Gleditschia, Caragana, &c. The pods generally ripen in September or October, but some not till November or December. The seeds may be kept in the pods till February, and then sown in beds, as described. At the end of two years the young trees may be transplanted.
The Formation and Management of Plantations.
Whether plantations of forest trees should be sown or planted, is a question which has been much discussed. It is readily allowed, that sowing is the natural mode; but man tries by art to supplement nature, and to obtain a higher rate of production by skill and labour. Some indeed have asserted that the timber of transplanted trees is never so valuable as that of sown ones, the reason alleged being, that the transplanted trees have lost their tap-roots. On examining the roots of full-grown trees, however, no taproot is ever found; on the contrary, those roots which proceed either directly or obliquely downwards from the base of the trunk, are uniformly much smaller than those which proceed horizontally, a few inches below the surface of the ground. The tap-root, therefore, is chiefly of use to the tree whilst young, and is larger in proportion to the part of plant above ground, in the first year, than in any succeeding year; and as the top of the tree and the lateral roots increase in size, the tap-root ceases to increase, till in ten or twelve years’ growth, it is found to be the smallest of the main roots of the tree. We assume, therefore, that a transplanted tree, other circumstances being the same, is in all respects as good as a seedling. Hence we conclude, that all artificial plantations ought, in the first place, to be made by planting, and at regular distances. We would carefully prepare the soil for the trees, removing the weeds afterwards for two or three years till the branches begin to cover the ground; in which state we should leave it during the growth of the plantation, only taking care to remove large weeds. This kind of tree culture, however, can only take place with advantage, on a tolerably level surface, where the soil is of the same nature throughout. Not to speak here of grounds destined for ornamental plantations, the great majority of plantations formed with a view to profit are necessarily on hilly and unculturable surfaces, and where there is probably a variety of soil, even in a limited space. The preparation to be given in such cases is under-draining; for to dig or trench the surface would render it liable to be washed away by heavy rains and thawing snow. Plantations under such circumstances must be formed by digging pits for each tree, and by selecting such kinds as are best adapted to the locality. This frequently occasions the use of a variety of trees in the same plantation, causing a more picturesque effect in the landscape and a more advantageous result in the production of timber. We have already stated that coniferous trees should be transplanted before they are four years old; but that broad-leaved trees may be moved at four, six, eight, or ten years’ growth; provided they have been transplanted every two years in the nursery, and that the 6oil is sufficiently deep and moist to bring the fibrous roots into full action the first summer. When strong plants of this kind are used they overcome the natural herbage immediately; and, if carefully planted in good soil, not one in a score will fail· Smaller plants, on the other hand, are apt to be choked by herbage, and to have their leaves and young shoots injured by insects. In a dry soil and subsoil, plants with a mass of roots cannot subsist the first year; and therefore smaller plants, once transplanted, are preferable. There are circumstances under which sowing is perhaps the only mode of forming plantations that can be adopted: as for example, in the dunes of Gascony, which by nearly a century of regularly continued sowings have been almost entirely transformed from drifting sandy wastes into forests of the cluster pine. In making plantations of this pine we should prefer sowing several seeds in every place where a plant was intended to remain, unless we could procure a sufficient number of plants of two years old in pots. If more than one came up, the rest should be removed the second or third year; and while the plants are young care must be taken that they are not choked by herbage. When steep rocky cliffs or stony hill-sides are to be covered with wood, sowing is the only mode that can be resorted to; the kinds of seeds to be sown may be selected according to the nature of the debris or the soil in the clefts of the rocks. Where the soil is good, broadleaved trees may be introduced; but where it is poor, the Scotch fir, larch, birch, mountain ash, and white beam tree are most suitable. Where there is no visible soil, two or three seeds, enveloped in a composition of moss, cow-dung, and loam, may be deposited in crevices, or among loose stones; acted upon by the rain, the seeds will vegetate, and find nourishment in the fragments of the ball in which they were enveloped.
Two important points connected with the formation of plantations are the distances at which trees should be planted, and the use of nurse-trees. As the strength of a plant depends on the number of its leaves, and their full exposure to light, it follows that the strongest young trees will be those which are clothed with branches and leaves from the groundupwards, and which have their leaves fully exposed on every side to light. The distance from each other at which trees should be placed in a plantation depends on the size and nature of the plants, and the soil, and situation. To have tall and straight stems, the trees are planted thickly (conifers more so than other kinds), about 4 to 6 feet apart; but when the lower branches of the plants interfere with one another, thinning should be commenced and continued from time to time. When the lower tier of branches shows symptoms of decay they should be removed by cutting close to the stem. This process of pruning has been condemned by many, particularly in soft-wood trees; but if practised early and judiciously it may be attended with benefit, especially when the part removed does not exceed an inch in diameter, or as long as the operation can be performed with an ordinary pocket-knife; the wound will heal quickly, and leaves no mark. If branches are a∣lowed to remain till they are 3 or 4 inches in diameter, and are then cut off at some distance from the bole (snagpruning) the timber deteriorates, the wound heals over in time, but the timber is either knotty, or unsound. Closepruning is performed by sawing off a branch close to the trunk or a leading branch. When the wound is large, a dressing should be applied to exclude air and moisture. For this purpose linseed oil, or three parts cow-dung and one part powdered lime, will be found useful. In the Royal Forests of England the branch of an oak is never removed unless special circumstances require it. Long experience has justified this system. Lateral branches which are growing with over luxuriance, and attracting too much of the sap of the plant, should be foreshortened, just as the lateral branches of a hedge are clipped when they extend too far. The only objection to this method of pruning is the amount of labour it entails. Mr M‘Nab of the Royal Botanic Garden, Edinburgh, has recently urged the advantage of stem-pruning of conifers, on the grounds that it encourages a free growth, and tends to make the trees hardy by exposing the bark of the stems to the freer action of the air. Stem-pruned trees also are less likely to be broken by a weight of snow lying on the branches.
For pruning, the following tools are required,—a pocket knife, hand-saw, chisel, and pruning shears; the two last are fixed on long poles. Thinning, carried out with care from time to time, is of the greatest consequence. The removal of weak and crooked supernumeraries prevents unnecessary exhaustion of the soil, while it admits the essential agents, air and light, which favour the expansion of lateral branches. If, however, the trees be thinned out too widely, the side branches become robust and the stem is not drawn up. The rule in thinning should be, to keep the trees clear of each other, so that the branches do not interlace, and the air circulates all round. The time when thinning should commence depends on local circumstances, and the species under cultivation. In a well-managed plantation the proceeds of thinnings in twenty years should go far to cover the expense of culture and interest of capital.
The next point to be considered is that of introducing nurse-plants into plantations. That these have a tendency to accelerate the upward growth of trees for a number of years there can be no doubt, but it is at the expense of the side branches and leaves. Evergreen nurses, such as the Scotch, silver, and spruce firs, improve the condition of a plantation by preventing the radiation of heat from the ground, by checking the growth of herbage, and by protecting the principal trees from high winds until they are thoroughly established in the plantation. The kind of tree which is to form the main crop having been fixed on, and the number that when full grown will stand on an acre or any given surface, they should be planted in their proper places, and the intervals filled up with the nurse-plants. As the nurses grow, and their branches touch the principals, let them be thinned, so as not to prevent the free growth of the principals: this should be done gradually. For example, it is customary to plant oak with coniferous nurses, and in the course of seven to ten years the nursee require a partial thinning to make way for the principal trees; at this date the pines will be fit for poles or rails. It often, however, happens that the nurses are allowed to remain too long, and the principal crop consequently suffers from the evils of overcrowding.
We have now alluded to some of the chief points connected with arboriculture, but the subject is of such extent that it could not be fully treated in the limits of this article. Our object has been rather to direct attention to general principles; and for fuller information we would refer those who desire a more practical and detailed acquaintance with the subject to the following works :—
The classic Sylva of Evelyn and the exhaustive Arboretum et Fruticetum Britannicum of Loudon should be in the hands of all students of Arboriculture. Selby’s History of Forest Trees, 1842; The Forester, by James Brown, 4th ed., 1871; Grigor’s Arboriculture, 1868; Du BreuiΓs Cours Elémentaire d'Arboriculture, Paris; Paradé’s Cours Elémentaire de Culture des Bois, Paris; Mathieu’s Flore Forestière, Nancy, 1860; and, j Hartig’s Lehrbuch für Förster, Stuttgart, 1861, are all useful books. Prize essays on special subjects are contained in the Transactions of the Highland and Agricultural Society, and instructive papers on various practical details are to be found in the Transactions of the Scottish Arbori-cultural Society. The Forest Flora of Northern India, by Stewart and Brandis, 8vo, with 4to volume of illustrations, London, 1874, contains a great amount of information on the culture of trees in India and the Himalayan region. For American trees see the North American Sylva, by Michaux, Paris, 1819; Trees and Shrubs of Massachusetts, by Emerson, Boston, 1846; and Trees of America, by D. J. Broune, New York, 1846. (IL C.)
Table Showing the number of Trees required to plant an Imperial or Scotch Acre, at distances of one to thirty feet. [table]
