Larch is scattered over a considerable part of the northern hemisphere, inhabiting nearly the same regions with the other Coniferæ. White larch, the kind[17] common in Britain, is found growing extensively on the alpine districts of the south of Europe, in Italy, Switzerland, Sardinia; this may be termed the European temperate species. Another, native to the country around Archangel, and extending from {77} Norway eastward through Russia and Siberia, of inferior size, may be styled the European Hyperborean. North America, like the old world, is said to possess a temperate and hyperborean species. The first, Black Larch (L. pendula), more generally extending along the longitudinal parallel of the United States; the other, Red Larch (L. microcarpa), along that of Lower Canada and Labrador. We have seen the American temperate attain 18 inches in diameter in Scotland, but it is much inferior in figure and growth, and also cleanness of timber, to the Appenine or European temperate, being covered with knots and protuberances. Though rough, the timber is said to be of excellent quality.
It is now upwards of 80 years since the larch, so common in Britain, was brought from the Appenines to Strath-Tay. The rapidity of its growth and striking novelty of appearance, assisted by the influence of the family of Athole (to a female of which some say we owe its first introduction), soon attracted general attention: it quickly spread over the neighbouring country, and was planted in every variety of soil and situation, from the unfitness of which, in most places of the low country, it is already fast decaying. About 40 years ago it began to be planted in many parts of Britain. It is now introduced into almost every new plantation in the two islands, and {78} the space of country covered by its shade is extending with a rapidity unparalleled in the history of any other ligneous plant.
Larch is generally conceived to be an alpine[18] plant, and its decay in the low country attributed to situation or climate. This idea seems to have arisen from its locality in Italy, and from observing it succeed so well in our alpine districts, not taking into account that the soil is different,—that it may be the soil of these districts which conduces to the prosperity of the larch, and not the altitude. Throughout Scotland, wherever we have observed the decay, it appeared to have resulted almost solely from unsuitableness of soil. We have witnessed it as much diseased on our highest trap hills, 1000 feet in altitude, as on a similar soil at the base. Yet the freeness from putrescency or miasma of the pure air of the mountain, {79} and deficiency of putrescent matter in the ground, or other more obscure agencies connected with primitive ranges, may have some influence to counterbalance unsuitableness of soil. It is not probable that the coolness and moisture of altitude would be necessary in Scotland to the healthy growth of a vegetable which flourishes under Italian suns, on the general level of the Appenine and on the Sardinian hills.
The rot, so general in growing larch, though sometimes originating in the bulb or lower part of the stem, seems to have its commencement most frequently in the roots. Thence the corruption proceeds upwards along the connecting tubes or fibres into the bulb, and gradually mounts the stem, which, when much diseased, swells considerably for a few feet above the ground, evidently from the new layers of sap-wood forming thicker to afford necessary space for the fluids to pass upward and downward—the matured wood through which there is no circulation approaching at this place within one or two annual layers of the outside. In a majority of cases, the rot commences in the roots which have struck down deepest into the earth, especially those under the stool; these having been thrown to a considerable depth by the young plant, as the tree enlarges, are shut out from aëration, &c. by the {80} superior increasing stool and hard-pressed earth underneath it; this earth at the same time becoming exhausted of the particular pabulum of the plant. It is, therefore, quite probable, from these parts of the roots being the weakest, that they will be most susceptible of injury from being soaked in stagnant water in the flat tills[19], starved during droughts in light sand, tainted by the putrid vapours of rich vegetable mould, or poisoned by the corrosive action of pernicious minerals. It may also be supposed that these smothered sickly roots, not possessing sufficient power or means of suction (endosmose), will be left out in the general economy of vegetation of the plant, thence lose vitality, and become corrupt. But this affords no explanation why the larch roots, under these circumstances, are more liable to corruption than those of other trees, or how the bulb itself should become contaminated. {81}
We have cut off the top, where the diameter of the section was about three inches, from sound young larch trees, and found a similar rot proceed downwards in a few months from the section, as rises from the diseased roots in improper soil. There is something favourable to the quick progress of this rot in the motion of the sap, or vitality of the tree; as, under no common circumstances, would the wood of a cut larch tree become tainted in so short a time.
The rot, though most general in trees which are chilled in wet cold tills, or starved in dry sand, or sickly from any other cause, is also often found to take place in the most luxuriant growing plants in open situations, branched to the ground, and growing in deep soil free from stagnating water. There must, therefore, be some constitutional tendency to corruption in the larch, which is excited by a combination of circumstances; and we must limit our knowledge for the present to the fact, that certain soils, perhaps slightly modified by other circumstances, produce sound, and others unsound larch, without admitting any general influence from altitude, excepting in so far as its antiseptic influence may go.
The fitness of soil for larch seems to depend more especially upon the ability the soil possesses of affording an equable supply of moisture; that is, upon its {82} mechanical division, or its powers of absorption or retention of moisture; and its chemical composition would seem only efficacious as conducive to this.
Soils and subsoils[20] may be divided into two classes. The first, where larch will acquire a size of from 30 to 300 solid feet, and is generally free of rot; the second, where it reaches only from 6 to 20 feet solid, and in most cases becomes tainted with rot before 30 years of age.
CLASS I. SOILS AND SUBSOILS FOR LARCH.
Sound rock, with a covering of firm loam, particularly when the rock is jagged or cloven, or much dirupted and mixed with the earth.—In such cases, a very slight covering or admixture of earth will suffice. We would give the preference to primitive rock, especially micaceous schist and mountain limestone. Larch seldom succeeds well on sandstone or on trap, except on steep slopes, where the rock is quite sound and the soil firm. {83}