The object of departing from the square, or round form, is to introduce the growing fibres of the young trees into the firm and poor soil, by degrees, and not all at once, as in the round or square-hole manner.
When a tree is planted in the round or square pit, surrounded outside of it by poor, hard soil, it is very much in the same situation as if its roots were confined in a tub or box.
The dove-tailing, so to speak, of the prepared soil, and of the moisture it will retain, with the hard, impenetrable soil by which it is surrounded, will gradually prepare the latter for being penetrated by the roots of the trees, and prevent the sides of the pit from giving the same check to those roots, which the sides of the pot or tub do to the plant contained in it. In the preparation of these holes, the lower spot, or hard-pan, should be thrown out, and ten to twelve inches of stone substituted, for the double purpose of drainage, and retention of moisture in dry weather. — H. W. Sargent.
In the actual planting of the tree, the chief point lies in bringing every small fibre in contact with the soil, so that no hollows or interstices are left, which may produce mouldi-ness and decay of the roots. To avoid this, the soil must be pulverized with the spade before filling in, and one of the workmen, with his hands and a flat dibble of wood, should fill up all cavities, and lay out the small roots before covering them in their natural position. When watering is thought advisable (and we practise it almost invariably), it should always be done while the planting is going forward. Poured in the hole when the roots are just covered with the soil, it serves to settle the loose earth compactly around the various roots, and thus both furnishes a supply of moisture, and brings the pulverized mould in proper contact for growth. Trees well watered when planted in this way, will rarely require it afterwards; and should they do so, the better way is to remove two or three inches of the top soil, and give the lower stratum a copious supply; when the water having been absorbed, the surface should again be replaced. There is no practice more mischievous to newly moved trees, than that of pouring water, during hot weather, upon the surface of the ground above the roots. Acted upon by the sun and wind, this surface becomes baked, and but little water reaches the roots; or just sufficient, perhaps, to afford a momentary stimulus, to be followed by increased sensibility to the parching drought.
With respect to the proper seasons for transplanting, we may remark that, except in extreme northern latitude, autumn planting is generally preferred for large, hardy, deciduous trees. It may commence as soon as the leaves fall, and may be continued until winter. In planting large trees in spring, we should commence as early as possible, to give them the benefit of the April rains; if it should be deferred to a later period, the trees will be likely to suffer greatly by the hot summer sun before they are well established.
The transplanting of evergreens is generally considered so much more difficult than that of deciduous trees, and so many persons who have tolerable success in the latter, fail in the former, that we may perhaps be expected to point out the reason of these frequent failures.
Most of our horticultural maxims are derived from English authors and among them, that of always planting evergreens either in August or late in autumn. At both these seasons, it is nearly impossible to succeed in the temperate portions of the United States, from the different character of our climate at these seasons. The genial moisture of the English climate renders transplanting comparatively easy at all seasons, but especially in winter, while in this country, our Augusts are dry and hot, and our winters generally dry and cold. If planted in the latter part of summer, evergreens become parched in their foliage, and soon perish. If planted in autumn or early winter, the severe cold that ensues, to which the newly disturbed plant is peculiarly alive, paralyses vital action, and the tree is so much enfeebled that, when spring arrives, it survives but a short period. The only period, therefore, that remains for the successful removal of evergreens here, is the spring.* When planted as early as practicable in the spring, so as to have the full benefit of the abundant rains so beneficial to vegetation at that season, they will almost immediately protrude new shoots and regain their former vigor.
Evergreens are, in their roots, much more delicate and impatient of dryness than deciduous trees; and this should be borne in mind while transplanting them. For this reason, experienced planters always choose a wet or misty day for their removal; and, in dry weather, we would always recommend the roots to be kept watered and covered from the air by mats during transportation. When proper regard is paid to this point, and to judicious selection of the season, evergreens will not be found more difficult of removal than other trees.
* It is surpassing strange that at this point, where Mr. Downing most clearly broke with English practice and most definitely indicated the grounds for the horticultural independence of America, his conclusions should not be sustained by later generations. The most experienced American planters of this day transplant evergreens freely in August, many of them preferring that month; and this procedure is successful even on the dry hot wind-swept central plains. — F. A. W.
Another mode of transplanting large evergreens, which is very successfully practised among us, is that of removing them with frozen balls of earth in mid-winter. When skilfully performed, it is perhaps the most complete of all modes, and is so different from the common method, that the objection we have just made to winter planting does not apply to this case. The trees to be removed are selected, the situations chosen, and the holes dug, while the ground is yet open in autumn. When the ground is somewhat frozen, the operator proceeds to dig a trench around the tree at some distance, gradually undermining it, and leaving all the principal mass of roots embodied in the ball of earth. The whole ball is then left to freeze pretty thoroughly (generally till snow covers the ground), when a large sled drawn by oxen is brought as near as possible, the ball of earth containing the tree rolled upon it, and the whole is easily transported to the hole previously prepared, where it is placed in the proper position, and as soon as the weather becomes mild, the earth is properly filled in around the ball. A tree, either evergreen or deciduous, may be transplanted in this way, so as scarcely to show, at the return of growth, any ill effects from its change of location.