using trees defined in 1944 yearusing trees - Using trees;
using trees - Lists are given below of the trees suited to certain particular purposes.
Light-Demanding TreesMany trees can only grow satisfactorily in strong light; they must therefore play the dominant part in any mixture of tree species, and cannot be used for under-planting. In thinnings, ample headroom must be allowed for each tree; any tree in danger of being suppressed or outgrown by its neighbours, may as well be cut out, as it will die as soon as its light supply becomes deficient. Light demanders usually cast a light shade only. They are useless for dense or dwarf hedges. Most are pioneer species, able to colonise treeless stretches of bare ground.
Strong Light-Demanders are: Ash, Poplar, Willows, Locust, Plane, Walnut, Sea Buckthorn, and Wayfaring Tree.
Pines, Larches, Big Tree, Japanese Cedar, Japanese Umbrella Tree, and Monkey Puzzle.
Moderate Light-Demanders are: Birch, Chestnut, most Oaks, Ailanthus, Horse-Chestnut, Laburnum, Lime, Liquidambar, Mulberry, Tulip Tree, trees of the Rose Tribe, Spindle, Elder, Purging Buckthorn.
Douglas Fir, Californian Redwood, Juniper, Swamp Cypress-, Maidenhair Tree.
Shade-Bearing TreesMany trees, although thriving in full light at most Stages of their growth, can tolerate overhead shade, particularly in youth. Thus, they may be allowed to fall behind quicker-growing light-demanders in mixtures, without suffering serious harm, and may be used for under-planting older stands of light-demanders. In thinnings, they may be allowed to stand fairly densely. Shade-bearers cast a dense shade and, as a rule, no other green plants can grow beneath them. Many are suitable for hedging. Most of them are secondary species in plant succession; that is, they follow light- demanders, grow beneath them, and often finally supplant them.
Strong Shade-Bearers are: Beech, Hornbeam, Evergreen Oak, Notofagus, Holly, Box, and Privet.
Hemlock, Silver Firs, Spruces, Yew.
Moderate Shade-Bearers are: Alder, Elm, Hazel, Sycamore, Strawberry Tree, Alder Buckthorn, Dogwood, and Guelder Rose. Cedars, Cypresses, Thuyas, and Incense Cedar.
Trees for TownsThe chief adverse factor restricting the growth of trees in towns, is coal-smoke, partly on account of its solid impurities, but largely because of the presence of sulphur dioxide, an invisible gas. In seaside or country-towns most species can be grown. The following short list gives trees known to thrive under the worst possible conditions in thickly built-up industrial areas. No evergreen conifer can thrive under such conditions.
Ash, Birch, Sycamore, Hybrid Black Poplars, Willows (especially Goat Willows), Lime, Plane, Wild Pear, Crab Apple, Hawthorn, Privet, Elder, and Maidenhair Tree.
Garden TreesAny tree may be grown in a garden, if the latter is big enough; most gardeners wishing to plant trees require a species which will attain a decorative form without becoming too large for its surroundings. For the small garden, light-demanders are the most suitable, as they qist such a light shade that other plants may be grown quite close to them; it is impossible to grow anything except spring bulbs beneath a strong shade-bearer such as beech, and nothing at all can be grown beneath a spreading yew.
In most cases it is worth while securing a special garden form of the tree desired, and suitable specimens may usually be inspected in commercial nurseries. Such varieties are very numerous, and the following list deals mainly with the commoner forms found also in the woodlands.
Beech, especially Copper, Maiden-Hair, and Pyramidal forms; Birches, Hornbeam, Norway Maple, Acer negundo; Evergreen, Red, and White Oaks; White, Grey, and Lombardy Poplars; Golden, Purple, White, and Weeping Willows; Golden and Purple Osiers.
White and Red Horse-Chestnuts; Laburnums; Locust; Liquidambar; Mulberry; Tulip Tree; Holly; Box; Strawberry Tree; most genera of the Rose Tribe - Crab Apples, Cherries, and Thorns (in especial varieties); Spindles (Euonymus species), Guelder Rose or Snowball Tree; Elder.
Monterey Cypress (Cupressus macrocarpa); nurserymen's forms of Lawson Cypress; Thuyas; Incense Cedar; Irish and similar pyramidal forties of Yew; Maidenhair Tree; Japanese Umbrella Tree; Cryptomeriajaponica (var. elegans only); dwarf foiras of Abies and Picea (Silver Firs and Spruces.)
Trees for HedgingTrees are frequently used for hedges, particularly when a higher screen is desired than could be obtained by growing shrubs. The following species are suitable:
Evergreen Broadleaves: Holly, Box, and Privet. (Only the' Holly will stop stock.)
Deciduous, Spiny Broadleaves, able to resist stock: Hawthorn, Blackthorn.
Unarmed Broadleaves with persistent brown leaves, attractive and sheltering in winter, but unable to resist stock: Beech, Hornbeam.
Evergreen Conifers: The following are more or less poisonous, and should not be used where livestock have access to them:
Yew, Monterey Cypress (Cupressus macrocarpa), Lawson Cypress, Thuyas.
Trees for the Seaside
The following trees are suitable for the first line of exposure to strong salt winds off the sea:
Sycamore, Sea Buckthorn, and famarisk. Monterey Cypress (C. macrocarpa), Maritime Pine, Stone Pine, Monterey Pine (Pinus radiata, or insigpis), Austrian Pine.
Less resistant are: Oak, Corsican Pine, Scots Pine, Pinus contorta.
Durable TimbersMost timbers may be rendered durable by artificial treatment with preservatives such as creosote, but some are naturally durable and require no such treatment. Durability in this case refers to outdoor conditions of dampness, or damping alternating with drying. Almost any timber will endure indefinitely if kept bone- dry; even the so-called " dry rot " requires moisture to become harmful.
Durable under all conditions are: Sweet Chestnut, heartwood of Oaks (but not Turkey Oak), Locust, Tulip Tree, Walnut, Cedar (true Cedarwood of the genus Cedrus), Cypress (true Cypress of genus Cupressus)y Douglas Fir, Larch, CaHfornian Redwood, Big Tree, Thuya, Incense Cedar, Yew, Swamp Cypress, Japanese Cedar.
Durable under water (or bone-dry) are: Alder and Elm.
Moderately durable are: Hemlock, and the resinous heartwood of Scots Pine.
FirewoodsThe following trees yield satisfactory firewoods for domestic burning:
Ash, Beech, Birch, Elm; Hornbeam, Maple, Sycamore, Oak, Locust, Lime, Apple, Pear, Mulberry, Plane, and Holly (Holly will burn even if unseasoned.)
Cedar, Cypress, Douglas Fir, Upmlock, Larch, Pine, Silver Fir, Spruce, Thuya, Incense Cedar, and Juniper.
The Weight of TimbersThe specific gravity of wood varies greatly according to the amount of water which any given sample of timber contains. This in its turn depends upon the degree of seasoning which the sample has undergone, the timber becoming progressively lighter as seasoning advances. With fully seasoned samples, the differences between different species found in Britain are not very marked.
Broad-leaved Timbers. Most of the commoner species have a specific gravity of around 7, each cubic foot weighing approximately 45 lb.
Heavier timbers are Holly (55 lb. per cubic foot) and Box (63 lb.). Box is frequently heavier than water. Both are hard, dense woods.
Lighter timbers are Alder, Horse-Chestnut, and Lime, all ranging around 35 lb. per cubic foot, and all soft. Very light are the Poplars and Willows, less than 30 lb. per cubic foot, both having a soft but tough-textured wood.
Coniferous Timbers are lighter on the average than the broadleaves, with a specific gravity of about *5, each cubic foot weighing some 30 lb. There is remarkably little difference between species, Yew, weighing 40 lb. per cubic foot, being the heaviest of common conifer woods, whilst Thuya plicata is the lightest, at 25 lb. per cubic foot.
In general, the heavier timbers are the stronger, but die ratio of strength for any given purpose to the weight of timber required to bear the strain, varies greatly with the various species, and can only be determined by experiment.
Identification of TimbersMany timbers may be identified by the naked eye or with the aid of a low-powered lens, provided that the sample shows a cross- sectional surface containing both heartwood and sapwood. The points to look for are hardness, colour, weight, and texture; presence and position of wood vessels, which show as small or large pores in cross-section; and the presence or absence of medullary rays, which show as thin lines radiating from the centre. The annual rings of growth are formed by the alternation of peripheral layers of spring and summer wood. The quick-grown spring wood is lighter, softer, and more porous than the slow- grown summer wood; the two together make up an annual ring.
Ring-porous Woods show large or numerous pores in their zones of spring wood.
Ash is pale yellowish grey in colour, with a small, pale-brown heartwood, and has large-pored springwood zones, and no apparent medullary rays.
Locust or Acacia wood may be distinguished by the very narrow sapwood zone, and the greenish hue of its heartwood; rays very fine.
The Elms have a distinct reddish tinge, and their vessels are grouped in irregular wavy lines, with fine medullary rays; usually cross-grained.
The Oaks, with a wide yellow sapwood, and a brown heart, are distinguished by their broad medullary rays.
Sweet Chestnut is similar, but the proportion of heartwood is greater, and the rays very fine or invisible.
Woods without Ringed Pores have a more dense and compact appearance than the foregoing.
The following have apparent medullary rays:
Plane is distinguished by its broad and numerous rays; colour pale brown; heartwood indistinct.
Beech also lacks a distinct heart, is pale-brown with a slight reddish tinge, and is homogeneous in texture apart from its broad medullary rays. On longitudinal sections these show as shining plates (radial cut) or as dark flecks (tangential cut).
Alder is soft, reddish-brown, with sparse broad rays and indistinct annual rings; heartwood indistinct.
Hornbeam, pale yellow, may usually be told by its extreme hardness, cross-grain, and horny texture.
Sycamore and Maple are white or light-coloured, with clearly marked annual rings, and many, narrow, clearly-defined and shining medullary rays.
Holly is white, sometimes with a greenish tinge, soft, and has thin white rings of summer-wood, with fine medullary rays; even- but short-grained.
Lime is reddish-brown, soft, with indistinct annual rings and fine rays.
Hazel, only found in small sizes, is reddish-brown and very hard.
Medullary rays are so fine as to be invisible in the following:
Apple and Pear with smooth, homogeneous, hard, red-brown wood.
Poplar and Willow, with light, soft wood, white sapwood and a darker heart.
Box, bright yellow, dense, homogeneous, heavy.
Bitch, pale yellow, brown, or fawn-coloured with a rough dusty surface when cross-cut, no marked heart, and a short-grained texture.
Other Broadleaved Timbers. Walnut is distinguished by its large vessels occurring in both spring and summer wood; heart- wood dark brown to black, sapwood pale brown.
Laburnum has a very dark heartwood contrasting strongly with its yellow sapwood.
Cherry, reddish-brown, has distinct medullary rays and a definite zone of spring wood formed of numerous fine vessels producing a distinctive texture.
Coniferous Timbers may usually be distinguished from Broad- leaves by their softer texture, lighter weight, absence of pores or vessels, and often by the presence of resin.
Spruce and Silver Fir lack a distinct heart and are only slightly resinous; both are pale brown.
Yew, also non-resinous, has a red heart and is hard, dense and heavy.
Thuya lacks resin, has a grey sapwood zone and a red-brown or pink heart; its extremely light weight also distinguishes it.
In Cypresses, aromatic oils with distinctive odours take the place of resin.
Amongst resinous softwoods with a distinct heart, Douglas Fir is distinguished by its narrow white sapwood zone, and dark brown or reddish-brown heart.
Larches have also a reddish heart, with a pale brown sapwood.
In True Cedars the brown heartwood is impregnated by an aromatic oil.
The Pines, most commonly met with of the conifers, fcnay usually be told by the comparative smallness of their red-brown heartwood, and their frequently coarse texture. They are very resinous, and the annual rings are well-defined.
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