Part 4 (2/2)
The stocks are cut into lengths of about ten inches, a gauge being used to secure uniform length. The cut at the bottom is made through a bud in such a way as to leave the diaphragm. The top cut is made as near ten inches from the bottom as possible, leaving about one and one-half inches above the top bud for convenience in grafting. The stock is then disbudded, taking both visible and advent.i.tious buds, the latter indicated by woody enlargements, to keep down the number of suckers.
[Ill.u.s.tration: FIG. 12. Bench-grafted cuttings of grape, showing both the cleft-graft and the whip-graft.]
The cion should be made with but one bud, thereby gaining the advantage of having every cion the same length so that all unions are at the same distance below the surface of the ground in the nursery.
The cion is made with about two and one-half inches of internode below the bud and one-half inch above, a sharp knife being the best tool for making the cuts.
Stock and cion cuttings are now graded to exactly the same diameters, this being necessary to secure perfection in the unions. Three methods of uniting stock and cion are ill.u.s.trated in Fig. 12. It suffices to grade by the eye into three lots--large, small and medium--but some nurserymen prefer to secure even greater accuracy by the use of any one of several mechanical gauges. The methods of uniting stock and cion may be described best by quoting Bioletti, from whom most of the details already given have been summarized:[5]
_Tongue grafting._
”When the stocks and scions are prepared and graded the grafter takes a box of stocks and a box of the corresponding size of scions and unites them. Each is cut at the same angle in such a way that when placed together the cut surface of one exactly fits and covers the whole of the cut surface of the other. The length of cut surface should be from three to four times the diameter of the cutting, the shorter cut for the larger sizes and the longer for the thinner. This will correspond to an angle of from 14.5 to 19.5 degrees. The cut should be made with a sliding movement of the knife. This will make the cut more easily and more smoothly.
”The cut should be made with a single quick motion of the knife. If the first cut is not satisfactory, a completely new one should be made. There should be no paring of the cut, as this will make an irregular or wavy surface and prevent the cuttings coming together closely in all parts.
”The tongues are made with a slow, sliding motion of the knife. They are commenced slightly above one-third of the distance from the sharp end of the bevel and cut down until the tongue is just a trifle more than one-third the length of the cut surface. The tongue should be _cut_, not _split_. The knife should not follow the grain of the wood, but should be slanted in such a way that the tongue will be about one-half as thick as it would be if made by splitting. Before withdrawing the knife it is bent over in order to open out the tongue. This very much facilitates the placing together of stock and scion.
”The stock and scion are now placed together and, if everything has been done properly, there will be no cut surface visible and the extremity of neither stock nor scion will project over the cut surface of the other. It is much better that the points should not quite reach the bottom of the cut surface than that they should overlap, as the union will be more complete and the scions will be less liable to throw out roots. If the points do overlap, the overlapping portion should be cut off, as in the Champin grafts.
”A skillful grafter, by following the above-described method, will make grafts most of which will hold together very firmly. Many of them would be displaced, however, in subsequent operations, so that it is necessary to tie them. This is done with raffia or waxed string. The only object of the tying is to keep the stock and scion together until they unite by the growth of their own tissues, so that the less material used the better, provided this object is attained. For the formation of healing tissue air is necessary, so that clay, wax, tinfoil or anything that would exclude the air should not be used. The tying material is pa.s.sed twice around the point of the scion to hold it down firmly, and then with one or two wide spirals it is carried to the point of the stock, which is fastened firmly with two more turns and the end of the string pa.s.sed under the last turn. The less string is used the more easily it is removed later in the nursery.
”Untreated raffia should be used for late grafts which are to be planted directly out in the nursery, but if the grafts are to be placed first in a callusing bed it is best to bluestone the raffia in order to prevent rotting before the grafts are planted. This is done by steeping the bundles of raffia in a three per cent solution of bluestone for a few hours and then hanging them up to dry. Before using, the raffia should be washed quickly in a stream of water in order to remove the bluestone which has crystallized on the outside and which might corrode the graft.
”Some grafters prefer waxed string for grafting. The string should be strong enough to hold the graft, but thin enough to be broken by hand.
No. 18 knitting cotton is a good size. It is waxed by soaking the b.a.l.l.s in melted grafting wax for several hours. The string will absorb the wax, and may then be placed on one side until needed. A good wax for this purpose is made by melting together one part of tallow, two parts of beeswax, and three parts of rosin.”
_Wire grafting._
”The merits claimed for this method are that it is more rapid, requires less skill, and does away with the troublesome tying and still more troublesome removal of the tying material. Practiced grafters can obtain as large a percentage of No. 1 unions by this method as by any other, and unpracticed grafters can do almost as well as practiced. Another advantage of the method is that the scions have less tendency to make roots than with the tongue graft.
”It consists essentially of the use of a short piece of galvanized iron wire inserted in the pith of stock and scion for the purpose of holding them together, thus replacing both tongues and raffia. It has been objected that the iron would have a deleterious effect on the tissues of the graft, corroding them, or causing them to decay. There seems, however, no reason to expect any such result, and vines grafted in this way have been bearing for years without showing any such effect.
”The preparation and grading of stocks and scions are exactly the same for this method as for the tongue graft.
”Stock and scion are cut at an angle of 45 degrees. A piece of galvanized iron wire two inches long is then pushed one inch into the firmest pith. This will usually be the pith of the stock, but it will depend on the varieties being grafted. The scion is then pushed on to the wire and pressed down until it is in contact with the stock. If the cuttings have large pith it is better to use two pieces of wire, one placed in the stock first and the other in the scion.
”The length of wire to use will vary with the size and firmness of the cuttings, but 2 inches will usually be found most satisfactory. Wire of No. 17 gauge is the most useful size.”
_Making bundles._
”If the grafts are to be planted out directly in the nursery, they may be simply laid in boxes or trays, covered with damp sacks, and carried out to be planted as soon as made. It is usually better, however, to place them for several weeks in a callusing bed before planting. In this case it is necessary for convenience of handling to tie them up into bundles. No more than twenty grafts should be placed in a bundle, and ten is better. If the bundles are too large there is danger of the grafts in the middle becoming moldy or dry.
”A stand is very convenient. It consists of a piece of board 12 inches, on one end of which is nailed a cleat 6 inches by 4 inches and under the other end a support of the same size. Two 4-inch wire nails are driven through the board from below, 4 inches apart and 5 inches from the cleat. Two other 4-inch nails are driven similarly at 1-1/2 inches from the other end. The grafts are laid on this stand with the scions resting against the cleat, and are then tied with the two pieces of bluestoned raffia that have previously been placed above each pair of nails. This arrangement insures all the scions, and therefore the unions, being at the same level, and puts both ties below the union where they will not strain the graft. The tying is more expeditious and less liable to disturb the unions than if the bundles are made without a guide.
”A skillful grafter will make about one hundred tongue grafts on cuttings per hour, or from sixty-five to seventy-five per hour if he does the tying as well. Wire grafts can be made at the rate of two hundred and fifty or more per hour, and by proper division of labor where several grafters are employed this number can be easily exceeded. These estimates do not include the preparation and grading of the cuttings.”
_Grafting rooted cuttings._
The cion may be grafted on a stock rooted in the nursery the previous season, much the same methods being used as with cuttings. This method is employed to utilize cuttings too small to graft, the added sizes attained in the nursery making them large enough, and in grafting on stocks which root with difficulty, thus saving the making of grafts which never grow. The stocks, in this method, are cut so that the cions may be inserted as the original cutting and not as the new growth. The roots, for convenience in handling, are cut back to an inch or thereabouts in length.
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