GRAFTING.

New Zealand Journal of Agriculture, Volume XIII, Issue 3, 20 September 1916, Page 193

GRAFTING.

W. H. TAYLOR,

Manager, Arataki Horticultural . Station

While grafting in itself is a very simple operation, so far at least as its mechanical performance is concerned, yet there are principles underlying it that cannot be ignored with impunity,. and in carrying it out a number of factors have to ,be understood if the operation is to be always successful. The work must also be accurately done. Neatness of the work and accuracy of the cuts both’ exercise great influence on the operation. The first requirement is to understand the principles. When ' these are grasped the operator knows exactly what is required; he knows when all conditions are right and exactly the kind of material to work on. A person may be able to put on a number of scions and get a large percentage of takes. But if one graft can be x put on right, why not all ? Simply because of the lack of accurate knowledge, or insufficient skill, rendering the work more or less speculative. Failures may occur from using improper wood as scions, from bad stocks, from bad workmanship, or doing the work too early or too late, or with scions not properly kept.

THE SCION.

It is generally recognized that ■ the scion should be in a more backward state’ of growth than the stock on which it is to be grafted. The reason why should also be understood, and then carelessness in this matter would be less frequent. A scion is really a tree without roots. It has ■no means of supplying itself with food that is the function of the stock. It should be clearly realized that as leaves come before roots, so top growth must be made by the scion before a union can be formed. The conditions required are that the stock shall be pumping up sap, which the scion does not immediately require, as the top growth has not begun. The junction of stock and scion being sealed up, the sap from the stock keeps the base of the scion fresh while the buds are breaking. As soon as the buds begin to push, their reciprocal action between scion and stock causes a union. Now, presuming that the scion were in a more forward state, with buds breaking when put on, it would require immediate sustenance; and as that could not be obtained, on account of there being’ as yet

no union, the growth of the scion might advance a little, but the whole would die. It may be asked, Why not put the scions on while the stock ' and scion are both dormant ? . This is frequently done, but the stock must not be dormant long or the scion will dry up.

It is important that the scions be kept in good condition until required 1 for working. They may be taken at any time while the trees are dormant. Mid-June is generally advised, but a month later is quite as good a time. The scions should be perfectly healthy wood of last season's growth. Choose wood of fair thickness—thin scions get but a feeble hold, and, moreover, are liable to wither if the weather should be hot and dry after grafting.

The scions should be buried in the, ground in a cool -place where the soil never becomes dry, but also never overwet; near a hedge is a good place. The scions should not be laid in bundles, but spread rather thinly, so that soil may come in contact with them all, - otherwise the bark may be injured by . insects and even sometimes become affected by fungi.

GRAFTS AND GRAFTING.

Grafting-time having arrived, the first thing to do is to get the necessary material ready —raffia for binding and wax for sealing up the union. Broad strands of raffia should be used, so as not to cut the bark. Wax I make of equal parts of beeswax and resin thinned with linseed-oil —roughly 2 lb. each of wax and resin, and half a pint of linseed-oil. Tests should be made to get the right proportion of oil. This preparation has the merit of simplicity, but as beeswax is now very expensive a receipe without beeswax may be given as follows : 8 lb. resin, 3 lb. . tallow, 3 lb. red ochre, 1 lb. Burgundy pitch; melt together in an iron pot, adding tallow and ochre last; do not make too hot. The wax or other'sealing compound must be applied in a melted state, not -too hot, and applied with a paint-brush. Wire the brush on before using, or it may melt off at the handle.

If young stocks are to be worked the scions are put on by the whip or tongue method. The cut in the stock and the scion should match each other. I do not like the cuts too short, as there is not enough surface to make a strong union ; they should be about 2 in. long. ■ Use a very sharp knife and cut clean, straight, and decisively, with no inequalities of surface. The fit should be perfect, so that when united stock and scion appear as though glued, together. When making the tongues do not start in the middle of the scion or stock. In the case of the stock start half-

way between the pith and the top ; and with, the scion commence half-way between the pith and the lower point of the scion. Cut into each about I in. When ' the tongue of the scion is pressed down into the stock the lower end will exactly meet the bottom of the cut in the stock, and -the upper parts of each will also meet, so that no cut surface is visible at either end.

I am aware that the manner of making the cuts for the whip graft as described above is not in accordance with the usual practice. The cuts are longer; .and although I do not object to the shorter unions, yet I prefer' the longer, as I consider that the greater surface of cambium layer effects a stronger union. It will be noticed that the strongest part of the scion so made is the centre wedge, which is usually the weakest part of the scion. I think this is beneficial, because there are four points of union in place' of two. In the grafting of grape-vines this style of sciorf is the only one that gives strong growth; short unions are only a subterfuge with grape-vines. ' •

The binding of the graft must be very firm, so as to keep all parts pressed close together.. Tie so that the binding will not become loose, or . the scion may rise in parts and a kind of callus form, preventing a perfect union. Further, if there is a lift anywhere, parts of the scion or stock may die, particularly the ends of either, which would not occur if contact were perfect. Care should be taken to use only wood with growth-budsno fruit-buds should be on the scion.

There is some difference of opinion as to where the cut should be made on the stock. Some think that a bud should be left near the apex. Personally I like to leave a bud in that position, because I consider there is more vitality in the wood close to a bud. I know, however, that it is not a matter of much importance; it is insignificant with a perfect fit and proper binding. With the scion it is different. In my opinion it is imperative to leave a bud at the base of the scion. A cut is made so that a bud is left close to the bottom. The bud, of course, is covered by the raffia and wax, but its influence is present, and this method seems to be much better than having vacant bark at the thin end of the cut. For another reason tight binding and perfect fitting is imperative. The wax is put on while hot. If the fit is not perfect, if there is the slightest opening between the scion and stock, the hot wax may enter, and then the scion may fail, but more likely there*.will be an imperfect union and a diseased appearance.

The scion should not be too long; two buds exposed make it quite long enough, and there is less left to the drying influences of sun and wind than if it were longer. It is desirable to make the top cut rather short and to wax it. over. This is not always

necessary, but I have had experience where no grafts would take unless the top was so waxed and drying thus prevented.

REGRAFTING OLD TREES.

The method of making the scions for this purpose is quite different; ' rarely is the whip graft used, . though it does come in occasionally. It is much . better to work on the limbs than on the main trunk. The latter must be used, however, if the limbs are too high up the. trunk, and also if there are not sufficient in the right position. ' Preparatory to grafting it is well to take most of the head from the tree a month or so before, so that the flow of sap may not be too copious. Some part ,of the head must be left, and should not be cut off till grafting is done. The method most frequently employed is the crown or rind graft. The bark only is lifted and the scion is slipped in, much in the manner of budding. ' The bark on one side only of the slit should be lifted ; the scion should have a thin strip - sliced off one edge to meet the bark on the side not lifted. The scion is prepared in a manner similar to the. whip-graft scion, but .no cuts are made in it. Secure a bud at the base as described for that method. These scions may be improved by cutting into them across the wood, then the downward -cut as before, the purpose being to make a shoulder to rest. on the stock. The advantage is less bulge of the scion and firmer fixing.

When working on the limbs some may be rather narrow for the rind graft. In such cases cut a triangular piece of wood out of the stock and make the scion to fit it exactly. These notch grafts are much better than rind grafts when the branch is not very thick yet too thick for the whip. The great advantage is that there is no broken bark, and it must be remembered that the raised edges of the bark always die. . Although the notch is a better graft than the rind, if many were to be put on time might be a bar, as the operation takes longer. Again, there may be branches not above I in. in diameter to be worked. For those the whip graft should be employed. Tying and waxing must be as with the' previously described method, and every cut surface should be waxed over, as such surfaces afford a ready means for the entry of diseasessilver-blight, &c. The question here arises as to which is best to cover withwax or clay. Personally, I am inclined to the wax, which I have always used, and I have done a considerable amount ; of this work.

A difficulty often arises in forming these worked trees. When the scions are placed around . the trunk there are likely to be two .causes of trouble. Firstly, the branches rise too straight' up ; secondly, the scions as • they swell to large branches may be too

close and come into contact with each other. Both troubles can be surmounted in this way : If wax is used for covering the scions the buds left at the base of the latter almost always grow. They break right through both raffia and wax and develop strong growth. Their union .with the old wood is perfect. These branches grow out at an angle from the trunk, this being partly caused by the sciongrowths above them. The higher shoots can be gradually removed and the basal ones left to make the tree. A proper spread is at once secured, and the butts of the branches do not collide with each other.

Note. —Figures of whip and notch grafts drawn from sketches by Mr. Taylor, illustrating methods followed by him. .