The Operation of Grafting is performed many ways, though none of them differs from any of the others in the main principle, which is that of bringing the under or inner bark of the scion to bear upon the same bark of the stock. The sap of the stock flows upward toward the scion, and it will flow on into the scion, provided it find no interruption. Here, therefore, is the nicety—to fit those two barks so closely, the one upon the other, that the sap shall proceed onward into the scion, just as it would have done into the amputated branch, causing the scion to supplant the branch. I shall only mention and illustrate two modes of grafting, viz., tongue-grafting and cleft-grafting. These two it is necessary for me to speak of separately, and thoroughly to describe, for they are not both of them applicable in all cases; the former being used in grafting on small-sized stocks and small branches of trees, and the latter on large stocks and large branches.
Tongue-Grafting.—(Fig. 58.)
Tongue-Grafting.—Suppose you have your stock of the proper age for grafting, you cut it off at three or four inches from the ground, and with a very sharp, straight, and narrow-bladed grafting-knife, cut a thin strip of bark and wood upward, from about two inches below your already shortened stock. Make this cut at one pull of the knife, inserting the edge rather horizontally, and when it has gone through the bark and into the wood a little short of the middle, pull straight upward, (2, a, b;) then at rather less than half way down this cut, and with the blade of your knife across the cut, and downward, cut a very thin tongue of not more than three eighths of an inch long, (2, c.) Proceed nearly in the same way with the bottom part of the scion; cut first a narrow strip of wood and bark out, but not putting the knife in horizontally, as you have done with regard to the stock, (at 2, a,) nor bringing it out straight to the end, to make a shoulder or angle, as you have done at (2, a b;) but make a sloping cut (1, a b,) of about the same length as the cut in the stock, or rather a little less if anything; then make a tongue (1, c) to correspond with that of the stock, but recollect that this must be cut upward instead of downward; then place the scion upon the stock, inserting the tongue of the scion into the tongue of the stock. Bring the four edges of bark, that is, the two edges of the cut in the top of the stock, and the two corresponding edges of the cut in the bottom of the scion, to meet precisely; or, if the scion be, in diameter, a smaller piece of wood than the stock, so that its two edges of bark can not both meet those of the stock, then let only one meet, but be sure that one meets precisely. But observe, that this can never be unless the first cut in the stock and that in the scion (2, a b,) and (1, a b,) be as even as a die, and performed with a knife scarcely less sharp than a razor. Take a common pruning-knife, and attempt to make a cut of this kind, and you will find when you come to fit the scion on, that, squeeze them together as you may, you will, in most cases, see light between the parts of the stock and the scion that you are trying to join, so effectually, as that the sap shall flow out of the one into the other, unconscious of any division at all! But I will not suppose anybody so ungain (as it is called in Hampshire) as to go about so nice an operation as this without being prepared with the proper instruments for performing it; and therefore, I now suppose the scion put on properly, and presenting the appearance as in (3, a.) But this is not all; the operation is not yet complete. The two parts thus joined must be bound closely to one another with matting, or bass, as the gardeners call it, (4.) A single piece tied on to the stock, will, if well done, almost insure the junction; but lest parching winds should come and rip up all vegetation, it is usual to put on besides the bandage of matting, a ball of well-beaten clay sprinkled over with a little wood-ashes or the fine siftings of cinders, to cover completely the parts grafted, that is, from an inch below them to an inch or so above them, (5;) and, even to prevent this ball of clay from being washed off by heavy rains, it is well to tie around it a covering of coarse canvass, or else to earth up the whole plant as you do beans or peas, drawing a little mound around it so as to reach nearly the top of the clay. Mr. Harrison prepares his grafting clay in the following manner: Take two parts of clay and one of horse-dung, free from straw, mix them together, and beat the mass until the whole is thoroughly incorporated, then temper it with a little water till it is reduced to the consistence of stiff paste. This composition never cracks on drying!
Future Treatment.—Something now remains to be said on the future treatment of the grafted plant. In a month's time at least, you will see whether the scion has taken; it will then be either bursting forth into leaf or be irrecoverably dead. In this latter case, take off immediately the canvass, clay, bandage, and dead scion, and let the stock push forth what shoots it pleases, and recover itself. In the former case, however, you must, as soon as the scion is putting forth shoots, cut off, or rub off, all shoots proceeding from the stock between the ground and the clay, as these, if suffered to push on, would divert the sap away from the scion, and probably starve it; then carefully stake the plant, that is, put a small stick into the ground at within three inches, or thereabouts, of the root, and long enough to reach a few inches above the scion, which you will tie to it slightly with a piece of wetted matting. This is really necessary, for when the shoots proceeding from the scion become half a foot long, they, with the aid of their leaves, become so heavy as, when blown to and fro by the wind, to break off immediately above the clay, or become loosened down at the part joined to the stock. The staking being done, you need do nothing more till near the end of June, when you should take off the whole mass of canvass, clay, and bandage, but be careful in taking off the clay not to break off the plant at the junction. It should be done by a careful hand, and after a day or two of rainy weather, as then the clay is moist and comes off without so much danger to the plant as when it is not. On taking off the clay, there is found a little sharp angle, left at the top of the stock; this should now be cut smooth off. The bark of the stock and that of the scion will heal over this, and the union is then complete. Lastly, it is frequently found that mould, and sometimes small vermin, have collected around the heretofore covered parts of the plant, according as the clay has been cracked by the sun. Rub off all mould with your fingers, (no instrument does it so well,) and kill all vermin in the same way; and it is not amiss to finish this work by washing the joined parts with a little soap and water, using a small paint-brush for the operation. All these things done, you have only to guard against high winds, which, if the plant be not staked, as is above described, will very likely be broken off by them; and, in this work of destruction, you will have the mortification of seeing the finest of your plants go first.
Cleft-Grafting.—(Fig. 59.)
Cleft-Grafting.—This is a species of grafting adopted in cases where the stock is large, or where it consists of a branch or branches of a tree headed down. In either of these cases, saw off horizontally, the part you wish to graft, and smooth the wound over with a carpenter's plane, or a sharp, long-blade knife, (1.)
Prepare your scion in this manner: At about, an inch and a half from the bottom, cut it in the form of the blade of a razor; that is, make it sharp on one side, and let it be blunt at the back, where you will also take care to leave the bark whole, (2, a.) Having thus prepared the scion, make a split (1) in the crown of the saw-cut downward for about two inches, taking care that the two sides of this be perfectly even. Hold it then open, by means of a chisel or a wedge, (or when the stock is but a small one, your knife,) and insert the scion, the sharp edge going inward, and the bark side or razor-back remaining outward, so that, on taking out the wedge or chisel, the cleft closes firmly on the scion, (3,) the two edges of bark formed by the cleft, squeezing exactly upon the two edges of bark formed by the blunt razor-back. To make the two barks meet precisely is the only nicety in this operation; but this is so essential, that the slightest deviation will defeat the purpose. In this sort of grafting, the stock on which you graft is generally strong enough to hold the scion close enough within its cleft, without the aid of binding, and then it is better not to bind; but as it is also necessary to prevent air circulating within the wounded parts both of the stock and the scion, use grafting-clay to cover them over so as to effectually exclude the air; and cover the clay with a piece of coarse canvass, wetting it first, and then binding it on securely. In this way, the stock being strong, you may insert several scions on the same head, by making several different clefts, and putting one scion in each; but this can only be to insure your having two to succeed, for if all the scions that you put on one head take, you must choose the two most eligible, and sacrifice the rest, as more than two leading limbs from such head ought not to be encouraged. The season for performing this sort of grafting, and the mode of preparing the scion, and the future treatment of the tree, are precisely the same as in tongue-grafting.
Crown, or Bark-Grafting is a very ready method of grafting upon large, uneven, old stocks and branches. It is practised somewhat later than the methods above described, that is, from the end of March to the third week in April, because, in that period, the separation of the bark from the wood is more easily affected; a circumstance of primary importance in this case. The tree is to be headed down, the cut being made horizontally, and the section bored quite even and smooth; then make a slit in the bark two inches in length, next with the handle of a budding-knife, carefully open the bark for about a quarter of an inch; then cut the scion about two inches in a sloping direction, in the form of a tongue, leaving the bark entire on the outside. The scion thus prepared, is pressed downward between the bark and the wood as far as the incision in the stock extends; the bark of the stock readily yields to the pressure employed, and the scion is supported in its situation by a few coils of bass-matting, the whole being surrounded by clay.