The many efforts to transplant trees of large size, and effect their successful thrift, have met with some instances of failure, owing to the want of due regard to the several requirements which tend to the success of the undertaking. In some instances, the injury to the roots on being extracted from the soil, and the after-neglect of precautionary trimming of the injured parts previous to again inserting them, have been the source from whence decay and disease have originated, to the destruction of the growth operated on. Again, the want of experience in the preparation of the soil suitable for transplants, and the preserving of the quietude of the tree till Nature enforces self-reliance and support by her production of agencies for this requisite, have been the cause of failure.
As the component material forming some soils varies from that of others, it is necessary that the planter be experienced in such matters, so as to come to a correct conclusion of the suitability of the soil to the growth of the species before he undertakes the removal of the tree from its ground. Generally the tree should be transplanted to soil of the same character as that from which it is taken: and this may be held as a criterion of its adaptability, that the nearer these soils approach in character the more confidence may be reposed in the future thrift of the tree.
One description of soil may be wet and porous, as the clayey sorts, while another may be dry and sandy. Each requires distinct preparation, conformable to many emergencies. The liability of any soil to retain moisture to excess necessitates that such methods be adopted as to prevent the flooding of the roots, which often occurs when the common system of hole-digging in clayey soils is resorted to, where the space excavated becomes a reservoir for the reception of surface-drainage and percolating moisture. When such soil is to be planted in, the best form to give the bottom of the excavation is convex or dome-shaped, so that any water which may pass through the soil is carried off to the sides on its reaching the more elevated portion of the bottom; and, to convey this casual flow to a distance beneath the root-bed, it will be well to have holes bored, say two in each pit, with a post-auger or other instrument. This will keep the roots from an excess of moisture, which would possibly be injurious to them. On no account should the bottom of a pit in which a tree of large size is to be planted have a concave form, as the weight of the tree and of the earth thrown in around it will likely act in such a manner as to induce a distortion of the roots by throwing them out of their natural position, ' which in most trees is at a slight angle from the stem downward.'
In instances where the roots of transplants, as in seedlings, are so long that they inconvenience the planting of the tree, they are cut off, not entirely, but to a necessary length, as it has been found that by so doing the setting of the roots is hastened by the emission of rootlets from the wounds so made. It may also be borne in mind that it does not follow from allowing numerous roots to adhere to a tree on its being transplanted that each and every one of them will draw sustaining food from the soil. On the contrary, either from disposition, or from decay caused by contact with uncongenial exposure, many become unsustaining; and this fact, therefore, enforces the necessity of due attention being paid to the growth above ground, which should be pruned to conform to the amount of nutriment likely to be supplied to it.
Another necessary precaution, to prevent the displacement of the roots, when once placed in the ground, and to keep the tree from excessive oscillation, has to be considered. The usual plan adopted for such an emergency is the placing of stakes close to the tree-stem, where they are lashed, their stability being relied upon to keep the tree from being so shaken as to cause any motion of its roots till they have taken firm hold in the ground. Another method in use is the staying of the stem by means of four lengths of wire which are made fast to it at a convenient height from the ground, and extended downward and outward till they reach the surface, where their ends are wound round pegs driven firmly, so as to keep the wire in a state of tension and the tree in an upright position in the centre of the circle so formed.
Roots of large trees, when placed in ground without pruning, are extended as nearly as possible conformable to their natural repose, and in this position are bound down by means of forked pegs. By the adoption of this plan a great deal of the necessity of outside supports, or stays, is lessened, as the pegs hold the roots so firmly that no danger of their displacement need be anticipated."