Certain varieties of our cultivated fruits are found to have a remarkable tendency to make an extended and very thrifty growth, which, continuing late into the autumn, would appear to expose the young trees to a very severe trial upon the access of the first cold weather, and we often find them very seriously injured under such circumstances; the bark is frequently split and ruptured for several inches near the ground. The twigs, still covered with abundant foliage, are so affected by the frost, that their whole outer surface is shriveled, and the inner bark and wood are browned; the latter often becomes permanently blackened, and remains as dead matter in the centre of the tree, for death does not necessarily ensue. Now intelligent nurserymen have endeavored to avoid losses from these causes, by budding such varieties upon strong well-established stocks, though they are aware that these are not more hardy than some of the cultivated varieties: a given number of seedling stocks has been found to suffer as much from the severity of winter, as do a similar amount of the grafted varieties taken at random.14 That the serious difficulty of bark-bursting occurs near the surface of the ground, does seem to be an argument of some weight in favor of budding or stock-grafting at a higher point. The earlier fruiting of budded trees than those which have been root-grafted, does not appear to be a well established fact, and therefore need not detain us; except to observe that the stocks, upon which the buds were inserted, might have been older by some years than the slip of root upon which the graft was set, so that the fruiting of the former tree should count two or three or more years further back than from the period of the budding. There are so many causes which might have contributed toward this result of earlier bearing, that we should not be too hasty in drawing conclusions in this matter.
The philosophy of budding is very similar to that of grafting. The latter process is performed when the plant-life is almost dormant, and the co-apted parts are ready to take the initiative steps of vegetation, and to effect their union by means of new adventitious cells, before the free flow of sap in the growing season. Budding, on the contrary, is done in the hight of that season and toward its close, when the plants are full of well matured and highly organized sap, when the cell circulation is most active, and the union between the parts is much more immediate than in the graft; were it not so, indeed, the little shield, with its actively evaporating surface of young bark, must certainly perish from exposure to a hot dry atmosphere. The cambium, or gelatinous matter, which is discovered between the bark and the wood when they are separated, is a mass of organizable cells. Mr. Paxton, using the gardener's expression, calls it the "pulp." Budding is most successfully performed when this matter is abundant, for then the vitality of the tree is in greatest degree of exaltation.
The individuality of the bud was sufficiently argued in the first section of this chapter, it need not now be again introduced, except as appropriately to remind us of the fact where the propagation depends upon this circumstance—the future tree must spring from the single bud which is inserted. Mr. A.T. Thomson, in his Lectures on the Elements of Botany, page 396, says:—"The individuality of buds must have been suspected as early as the discovery of the art of budding, and it is fully proved by the dissection of plants. * * Budding is founded on the fact, that the bud, which is a branch in embryo, is a distinct individual. It is essential that both the bud and the tree into which it is inserted should not only be analogous in their character, as in grafting with the scion, but both must be in a state of growth at the time the operation is performed. The union, however, depends much more upon the bud than upon the stock—the bud may be considered a centre of vitality—vegetative action commences in the bud, and extends to the stock, connecting them together."—"The vital energy, however, which commences the process of organization in the bud, is not necessarily confined to the germ, nor distinct from that which maintains the growth of the entire plant; but it is so connected with organization, that when this has proceeded a certain length, the bud may be removed from the parent and attached to another, where it will become a branch the same as if it had not been removed."
The season for budding has already been indicated in general terms, it is usually done in mid-summer and the early part of autumn, reference being had to the condition of the plants to be worked; these should be in a thrifty growing state, the woody fibre should be pretty well advanced, but growth by extension must still be active, or the needful conditions will not be found. The "pulp" must be present between the bark and the wood of the stock, so that the former can be easily separated from the latter; in the language of the art, the bark must "run;" this state of things will soon cease in most stocks, after the formation of terminal buds on the shoots. The success of spring budding, however, would appear to indicate that the cambium layer is formed earlier in the season than is usually supposed; for whenever the young leaves begin to be developed on the stock, "the bark will run," and the buds may be inserted with a good prospect of success. In this case we are obliged to use dormant buds that were formed the previous year, and we have to exercise care in the preservation of the scions, to keep them back by the application of cold, until the time of their insertion.
The condition of the bud is also important to the success of the operation. The tree from which we cut the scions should be in a growing state, though this is not so essential as in the case of the stock, as has been seen in spring budding—still, a degree of activity is desirable. The young shoot should have perfected its growth to such an extent as to have deposited its woody fibre, it should not be too succulent; but the essential condition is, that it should have its buds well developed. These, as every one knows, are formed in the axils of the leaves, and, to insure success, they should be plump and well grown. In those fruits which blossom on wood shoots of the previous year's growth, as the peach and apricot, the blossom buds should be avoided; they are easily recognized by their greater size and plumpness. In cutting scions, or bud-sticks, the most vigorous shoots should be avoided, they are too soft and pithy; the close jointed firm shoots, of medium size, are much to be preferred, as they have well developed buds, which appear to have more vitality. Such scions are found at the ends of the lateral branches. These need immediate attention, or they will be lost. The evaporation of their juices through the leaves would soon cause them to wither and wilt, and become useless. These appendages are therefore immediately removed by cutting the petioles from a quarter to half an inch from the scion; a portion of the stem is thus left as a convenient handle when inserting the shield, and this also serves afterward as an index to the condition of the bud. So soon as trimmed of their leaves, the scions are tied up, and enveloped loosely in a damp cloth, or in moss, or fresh grass, to exclude them from the air. If they should become wilted, they must not be put into water, as this injures them; it is better to sprinkle the cloth and tie them up tightly, or they may be restored by burying them in moderately moist earth.
The early gardeners were very particular as to the kind of weather upon which to do their budding. They recommended a cloudy or a showery day, or the evening, in order to avoid the effects of the hot sunshine. This might do in a small garden, where the operator could select his opportunity to bud a few dozen stocks; but even there, wet weather should be avoided, rather than courted. But in the large commercial nurseries, where tens of thousands of buds are to be inserted, there can be no choice of weather; indeed, many nurserymen prefer bright sunshine and the hottest weather, as they find no inconvenience arising to the trees from this source. Some even aver that their success is better under such circumstances, and argue that the "pulp is richer."
Most trees in their mature state make all their growth by extension or elongation very early in the season, by one push, as it were; with the first unfolding of the leaves, comes also the elongation of the twig that bears them. In most adult trees in a state of nature, there is no further growth in this way, but the internal changes of the sap continue to be effected among the cells during the whole period of their remaining in leaf, during which there is a continual flow of crude sap absorbed by the roots, and taken up into the organism of the tree to aid in the perfection of all the various parts, and in the preparation of the proper juice and the several products peculiar to the tree, as well as its wood and fruits. When all this is transpiring within its economy, the tree is said to be in its full flow of sap; at this stage the young tree is in the best condition for budding,