CHAPTER XII

TREES BEST ADAPTED FOR VARIOUS SOILS

There is, perhaps, no soil so bad and barren that it may not be rendered either profitable or ornamental by judicious planting; but, as might be expected, there is often a great want of knowledge as to the proper kind of trees to be chosen to suit a particular soil. In looking over a large extent of woodland one will often be struck with the great disproportion in size of the individual trees of a species; but it will generally be noticed that where the largest and healthiest occur the tree is usually growing upon its own soil, and is found to be flourishing at the expense of all around it. Thus the finest oaks will be found where the soil is deep and loamy, resting on clay; beech, and the Austrian pine (_Pinus austriaca_) upon a calcareous gravel, resting on a bed of chalk; ash and elm on a dampish, loamy gravel; birch in a light, black loam, with a gravelly substratum; Spanish chestnut, in a good loamy or gravelly soil, not too damp; the Scotch and Corsican pines (_P. sylvestris_ and _P. laricio_) at fairly high altitudes, and in gravelly, well-drained soils; and the Cluster and Aleppo pines (_P. Pinaster_ and _P. halepensis_), in almost pure sand on the sea-coast. Some trees grow rapidly for a few years in almost any soil, but where the soil is unsuitable they generally show signs of distress after a time, make little or no progress, and ultimately become stunted and ill-grown. Should the soil be very unfavourable, they die outright. Instances of this are, unfortunately, far too common wherever one travels over the country, owing to trees of a kind that are utterly unfitted for the particular class of soil being planted in a haphazard kind of way, without any consideration of their individual requirements. For all practical purposes with reference to tree-culture, soils, generally speaking, may be divided into six distinct classes—peaty, chalky or limey, gravelly, clayey, loamy, and such as contain ironstone, coal, etc.

(1) =Peat.=—Few trees will succeed well on an unreclaimed peat bog, but, where draining and soiling have been attended to at the outset, the number that grow and produce a fair amount of valuable timber is almost without limit among our generally cultivated species. Among conifers that have proved themselves suitable for bog planting are the larch, Scotch pine, and common and black spruces (_Picea excelsa_ and _P. nigra_). The larch grows rapidly, and is less subject to disease on peaty than any other soil—indeed, up to a few years ago, I cannot remember having seen a trace of any of the diseases which have rendered the life of the tree so precarious of late years in this country. In thinning a larch plantation of fully sixty years’ growth I found the trees felled to be perfectly healthy, and of exceptional quality, with, on an average, 72 ft. of wood in each. The subsoil in this case was clay, and the bog, previous to being planted, had been cut over for fuel. The Scotch pine grows almost as freely as the larch—the average in over fifty trees measured being about an eighth less—under similar conditions. Natural reproduction of the Scotch pine goes on so rapidly that it must be considered one of the very best trees for planting on peat bog. The spruces are excellent trees for planting on reclaimed peat bog, where they produce a fair amount of timber and afford excellent shelter to other trees. Of hardwoods, the beech is one of the best for bog planting, as it grows rapidly and produces a large amount of clean timber. The alder grows luxuriously on peaty soils, and shows no traces of disease or canker. Another excellent bog tree is the Gean or Wild Cherry, and this may likewise be said of the holly. Ash and oak are not generally of large size, nor are they always healthy on peat bog, even when it has received a great amount of attention in the way of reclaiming. Birch, lime and poplar of various kinds are all suited for planting on well-drained bog.

Among coniferous trees, a large number are well suited for planting in reclaimed peat bog. By way of experiment I have planted specimens of various kinds in newly-formed plantations, and in nearly every case the trees have grown well, particularly when partially sheltered. _Cupressus macrocarpa_ is one of the best, and not one whit behind it are _C. Lawsoniana_ and _C. goveniana_. _Wellingtonia gigantea_ and _Sequoia sempervirens_ have done well, while _Pinus laricio_ and _P. austriaca_ grow freely. I find that the majority of the recently introduced conifers do well on prepared peat bog—that is, where a quantity of loam has been incorporated with the bog and all superfluous moisture drained away.

(2) =Chalky Soils.=—The beech is peculiarly well suited for planting in chalk districts, for it will grow and produce a large quantity of excellent timber where but a few inches of loam overlie the chalk. It is a fact that, in Southern England particularly, in order to find where the chalk beds lie, one has only to be guided by the line traced out by the largest and most luxuriant beeches.

The beech will grow freely enough on almost pure chalk, but it certainly flourishes best where loam, say, from 1 ft. to 3 ft. in depth, overlies the chalk, or is incorporated with it, as on the Chiltern Hills.

The Norway maple (_Acer platanoides_) revels in a chalky soil, and so does _A. colchicum rubrum_. These are both handsome, hardy, large-growing trees, and well suited for extensive forest-planting under certain conditions of soil. White poplar (_Populus alba_) is an excellent tree for planting in chalky districts—indeed, it is surprising to see to what an immense size it attains on almost pure chalk.

Other poplars that do almost equally well on the chalk formation are _P. monilifera_ and _P. canadensis_, both excellent, free-growing trees. Elms, particularly the Huntingdon and the American, grow rapidly, and attain to a large size, where but a small quantity of loam is present in the chalk. The wych elm grows freely in chalky districts, and this may also be said of the common and silver-leaved lime. False acacia (_Robinia Pseud-acacia_) is an excellent tree for chalky soils, and there attains to a greater size than in even the richest of loams. The alder and birch also thrive with vigour on chalky soils. Indeed, most trees which in a state of nature grow in damp or marshy soils, are well suited for planting where chalk is the component of the main soil, and this is explained as follows:—Chalk, although sufficiently porous to allow water to percolate through it, has, like all other calcareous matter, a strong attraction for water, and acts like a sponge in holding it in considerable quantity for a very long time. Among the conifers that are suitable for chalky soils the Spanish fir (_Abies Pinsapo_) is one of the best. In the chalky districts of Southern England it thrives with unusual luxuriance. The Mount Enos fir (_Abies cephalonica_) is, likewise, well adapted for growing in chalky districts. Of evergreen trees that succeed well on chalk the number is well known to be limited, and it is important that two such beautiful conifers as the Spanish and Mount Enos firs should there find their most congenial home.

Both the Scotch and Weymouth pines (_Pinus sylvestris_ and _P. Strobus_) are well suited for planting on chalk, and many fine examples of both may be seen on the chalky reefs of Kent and Surrey.

The common Yew grows freely where hardly a particle of soil overlies the chalk formation.

The Giant Arborvitæ (_Thuja gigantea_) is peculiarly suitable for planting in chalky soils: and the Lebanon Cedar (_Cedrus Libani_) is never found in greater perfection than when growing in the chalk with a fair depth of loam atop.

_Wellingtonia gigantea_ also does well.

(3) =Gravelly and Sandy Soils.=—The Corsican pine is an excellent tree for planting on gravelly soils, and some of the largest and finest specimens in this country are growing in a disused gravel-pit, and this may also be said of the Douglas fir (_Pseudothuga Douglasii_).

The Scotch pine is well known to be one of the best conifers for planting in gravelly soils, where it reproduces itself in great numbers, when the conditions of growth are at all favourable.

_Pinus Pinaster_, the cluster pine, is, perhaps, one of the most valuable conifers for planting either in gravelly or sandy soils. The great value of the tree in reclaiming sandy tracts, both at home and abroad, has been so often described that further reference here is not required. The Aleppo pine is a good companion to the Pinaster, and grows with great freedom in a sandy or gravelly soil, within the influence of the sea. Gravelly soil also suits the Weymouth pine, on which it produces a fair quantity of very resinous timber. Both the beech and oak produce a large volume of timber on poor gravelly and sandy soils.

(4) =Clay Soils.=—The soil here referred to is genuine clay, devoid of stones, and without a particle of sand or loam in it.

It occurred on the slopes, and for some considerable distance along the sides of one of the park roads on an estate in England.

This is recorded simply to show what species of trees are best able to succeed when planted in pure clay. The pits, in this case, it may be well to mention, were dug and the soil thrown loosely up for a month previous to planting, but no soil was added to the stiff clay. Nearly one hundred kinds of trees and shrubs were used, but out of all these not more than eight are doing well, the others having gradually died out, or become so rusty and miserable looking that their removal was compulsory. First among the trees that have succeeded is the giant arborvitæ (_Thuja gigantea_), which seems to revel in what is generally considered the most unkindly of soils. _Cryptomeria japonica_ has also done well, but the trees of this kind, though bushy and well-furnished, have grown at a comparatively slow rate.

_Cupressus macrocarpa_ also has done fairly well: the growth certainly has not been rapid, but for all that the general appearance of the trees is the reverse of what one might expect from the unfavourable nature of the soil. The Indian Cedar (_Cedrus Deodara_) we have found to be peculiarly well suited for planting in clayey soils, the bright silvery tint that is so characteristic of this cedar when well grown being discernible in the clay-grown specimens. _Pinus austriaca_ has, in a few instances, done well, the foliage being ample and of the usual dark yew-green. Amongst shrubs the double-flowered gorse (_Ulex Europæus_, fl. pl.) has done best of any—indeed, it has grown and increased freely, and would seem to be quite as much at home as in its natural element—a dry, gravelly bank. These may be considered as the trees that have succeeded best in stiff, clayey soil. Few of the pine tribe did well, and this may also be said of the spruces, cypresses, yews, junipers, arbutus, dogwood, cotoneaster, hollies, and others planted.

It is, of course, far from advisable to plant trees or shrubs in such unkindly soil without first adding other of better quality; but it is of great value to know that there are a few trees and shrubs that will thrive almost in defiance of the stubborn and unkindly nature of a stiff clay soil.

(5) =Ironstone Soils.=—The particular class of soil to which I refer, and which in several districts occurs in plenty, is on the coal and ironstone formation, where the top soil is usually shallow, and the subsoil consists of a loose, yellowish rag that is largely impregnated with iron. In most places but a very small quantity of soil exists, and that is of the poorest description, varying in depth according to the lie of the measure. The Spanish Chestnut is one of the very best trees for this soil, growing with freedom, and producing a fair amount of good timber, while its appearance indicates perfect health.

Birch and beech do well, although neither of them attains to a large size. The latter reproduces itself freely from seeds, and soon spreads wherever a footing can be got. Sycamore grows freely, particularly where the pan is broken up, and produces a small quantity of good timber. Another tree that seems perfectly at home on the coal and ironstone is the wild cherry, for there it grows to a fair size, flowers freely, and produces excellent timber. Larch cannot be recommended for this soil, but in places where a small quantity of loam overlies the coal and ironstone it grows with great freedom for a number of years, and the timber, if cut early, is of good quality. The common spruce soon dies out, although it may grow freely enough for a number of years after being planted, and wear a healthy appearance. Oak and ash do fairly well, but they rarely attain to a large size or produce first-class timber. Rhododendrons almost revel in this soil, and some of the largest and healthiest are growing with their roots in close contact with the coal and ironstone.

=Shrubs for Hot and Dry Soils.=—The Bladder Senna (_Colutea arborescens_) is one of the most useful of shrubs for planting in poor, hot, dry soils, and not only will it succeed and flower well in these, but it is equally valuable for using where the air is chemically impure, and for that reason has few equals for the town or city shrubbery. _C. cruenta_ is also valuable in a similar way. The Sea Purslane (_Atriplex halimus_) is another valuable shrub for planting in hot and dry situations as is _Caragana arborescens_, the native Barberry (_Berberis vulgaris_), many forms of Genista and Cytisus, _Spartium junceum_, and the double flowering Gorse. Another excellent shrub is the Box Thorn or Tea Tree (_Lycium Europæum_) which is useful for covering an arid hot bank, several species of Cotoneaster, particularly _C. horizontalis_ and _C. microphylla_, and the neat and curious _Muchlenbeckia complexa_. Helianthemums also do well, so does the Venetian Sumach (_Rhus cotinus_), and several varieties of bramble, but especially the double pink flowering form. The Rest Harrow (_Ononis arvensis_), a native shrubby plant of great floral beauty, also does well; while the little known _Celastris articulatus_ should not be neglected in hot and dry situations. Other good shrubs for hot dry banks are _Potentilla fruticosa_, the Tamarisk and _Juniperus tamariscifolia_.

=Concluding Remarks.=—In conclusion, it may be pointed out that it is only by a careful selection of soil that we may expect tree planting to be successful, and I have no hesitation in saying that many failures can be clearly traced to errors of judgment in the selection of trees for planting on particular soils. The subject is a wide and complicated one, and it must be admitted that very perplexing diversities occur with the same kinds of trees on what, to all appearance, is the same class of soil. There are, of course, other considerations beyond the soil itself which must be taken into account, such as aspect, elevation, and whether the ground is inland or on the coast.

With reference to some of the newer conifers it must be admitted that soil and situation have a wonderful influence on their successful culture, and this applies in particular to such kinds as are not perfectly hardy and liable to injury by unseasonable frost. The too common practice of selecting warm and sheltered spots for such is, in the main, to be condemned.

It may be said that _Abies cephalonica_ and _A. Pinsapo_ are not worth growing, and in many places they are not, but when planted on limestone or chalk they are highly ornamental.

The same holds good in the case of _Tsuga Mertensiana_, _Picea Sitchensis_, and _P. excelsa_, which are rarely seen in good form except on soil of a peaty description.

Every one at all interested in trees and shrubs knows that there are certain kinds which in a state of Nature are only found growing in a peaty soil, mixed it may be more or less with sand, and any attempt to cultivate them in other soils is productive of very unsatisfactory results.

Who would ever think of planting the so-called American or peat plants, Cape Heaths, etc., amongst gravel or chalk, or Rhododendrons where lime is present in the soil? And these facts show us that there is something in the composition of certain soils only suitable for the requirements of a certain class of plants.

Another curious fact is this, that when growing on certain soils the timber of one species of tree is found to be far more durable than in others.

Deep loamy soil and soft peat produce timber that is usually of a second-rate description, being deficient in firmness.

By studying the geological strata of a district much useful information may be learnt regarding the trees best suited for planting.

The following alphabetical table will serve to show at a glance the trees that have been found best suited for planting in the class of soil under which they are enumerated:—

RECLAIMED PEAT BOG.

_Hardwoods._

Alnus glutinosa Populus alba —— —— imperialis —— balsamifera —— —— laciniata —— canadensis Betula alba Quercus Robur, and vars. Cerasus Padus Salix fragilis —— vulgaris Tilia europeæ Fagus sylvatica Ulmus alata —— —— purpurea —— montana

_Conifers._

Abies concolor Larix Kæmpferi —— bracteata Pinus austriaca —— nobilis —— excelsa —— Nordmanniana —— laricio Cedrus Deodara —— sylvestris Cryptomeria japonica Retinospora ericoides Cupressus Goveniana —— plumosa —— Lawsoniana —— —— aurea —— macrocarpa Taxus baccata Juniperus chinensis Thuja gigantea —— recurva —— occidentalis —— Sabina Thujopsis borealis Larix europeæ Wellingtonia gigantea

CHALKY OR CALCAREOUS.

_Hardwoods._

Acer colchicum rubrum Cerasus Padus —— dasycarpum Cratægus (nearly all) —— Negundo Cytisus Laburnum —— platanoides Fagus sylvatica —— Pseudo-platanus —— —— purpurea Æsculus Hippocastanum Fraxinus excelsior —— rubicunda —— Ornus Alnus glutinosa, and vars. Gleditschia sinensis Amelanchier Botryapium —— triacanthos Amygdalus communis Koelreuteria paniculata Betula alba Populus alba Castanea vesca —— balsamifera Catalpa bignonioides —— canadensis

Populus monilifera Quercus Turneri —— tremula Robinia Pseud-acacia, and vars. Pyrus Aria Salix alba —— Aucuparia Tilia argentea —— Malus floribunda —— europeæ —— spectabilis Ulmus alata Quercus Ilex —— glabra —— Mirebecki —— montana —— rubra Virgilia lutea

_Conifers._

Abies Amabilis Pinus austriaca —— magnifica —— Cembra —— nobilis —— excelsa —— Nordmanniana —— laricio —— Pinsapo —— Pinaster —— Webbiana —— Strobus Cedrus atlantica —— sylvestris —— Deodara —— tuberculata —— Libani Retinospora ericoides Cupressus Lawsoniana —— filicoides —— macrocarpa —— plumosa Juniperus chinensis —— —— aurea —— communis Salisburia adiantifolia —— Sabina Taxus baccata, and vars. —— —— tamariscifolia Thuja gigantea Larix europeæ —— Lobbii —— Kæmpferi —— occidentalis —— leptolepis —— Warreana Picea excelsa Thujopsis borealis

GRAVELLY AND SANDY.

_Hardwoods._

Alianthus glandulosa Morus nigra Alnus cordata Platanus occidentalis Betula alba Populus Bolleana Carpinus betulus Quercus Robur, and vars. Fagus sylvatica —— suber —— —— purpurea Robinia Pseud-acacia Fraxinus Ornus Sambucus nigra Gleditschia horrida Tilia europeæ Ilex, many vars. Ulmus alata Juglans cinerea —— campestris —— nigra —— montana Magnolia acuminata Virgilia lutea

_Conifers._

Juniperus communis Pinus Pinaster —— Sabina —— pumilio Pinus austriaca —— sylvestris —— halepensis Taxus baccata —— laricio Thuja gigantea

CLAY.

Carpinus betulus Quercus Ilex Castanea vesca —— pannonica Cryptomeria elegans —— Robur —— japonica Thuja gigantea Gleditschia triacanthos —— Lobbii

IRONSTONE AND COAL.

Acer Pseudo-platanus Larix europeæ Betula alba —— —— pendula Castanea vesca Pinus Cembra Cerasus Padus —— Montana Cupressus Lawsoniana Quercus Robur Fraxinus excelsior Thuja gigantea Juniperus communis Ulmus montana