It is advisable to label scions before they are stored to avoid the confusion that will result if they are mixed. I find that the best method of doing this is to get a sheet of zinc, from 20 to 30 gauge thick, and cut it into strips one inch wide by one and three-quarters inches long. I bore a small hole in one corner of each tag, through which I thread 18-gauge copper wire, doubled and with the bottom loop folded over (see page 40). In preparing these tags, it is important to remember that both wires must pass through the hole in the metal tag, otherwise, the slight movement due to winds will cause the metal to wear through. Two wires prevent this action indefinitely. Since a small wire cuts through a zinc tag in one or two years, heavy wire must be used. Wire such as I have indicated is satisfactory. I print the necessary information on each tag with a small, steel awl, and such labels are still legible after twenty-five years. Copper, brass or aluminum would also make good tags, but these metals are more expensive. Of course, these tags may be used for small trees as well as grafts and scionwood and it is always well to do a good job of labeling all work, since many errors may result from disregard to this important detail.
In the north, the time to graft nut trees is when the cambium layer of the host, or stock, is active, which is usually during the entire month of May. This cambium layer consists of those cells lying just inside of the outer bark, between it and the woody part of the tree. When these cells are active, the inner side of the bark feels slippery and a jelly-like substance can be scraped from it. Although this is the state in which the stock should be for grafting, the condition of the scions should be almost the opposite, rather dry and showing no signs of cambium activity. The bark should cling firmly to the woody part of the scions, whereas the bark of the stock should slip off readily. Another good and fairly satisfactory rule is never to graft the stocks of nut trees until after the young leaves appear.
In grafting young nursery trees not more than an inch in diameter, the whole tree is cut off at any distance from the ground convenient to the nurseryman. Sometimes they are cut within a few inches of the ground, sometimes two or three feet. In my work, I like to keep the scions as high above the ground as I can. When the top of a stock is cut off, there is a great deal of sap pressure and the tree bleeds. It is a poor policy to attempt grafting while this is happening. Rather, one should cut the tops off, then wait for several days before inserting any grafts. Tools must be kept very sharp. A good grafting knife is sharpened on one side only, so that the blade is flat along the side which lies next to the cut made on the scion when it is trimmed. If unaccustomed to handling a knife, one can obtain more accurate results by using a small plane. I do this by holding the scion firmly in my right hand and pulling it toward me, against the cutting edge of the plane which is held in the left hand. Illustrations show how this is done.
The only disadvantage in using a plane is that one must exchange it for a knife to make the receiving cut in the stock before inserting the graft. This necessitates exposing the graft to the air for a longer time than does using a single instrument.
Spring budding is done during the same period as grafting. Bud wood is usually much larger in diameter than scionwood, for it is easier to remove buds from big branches than from wood only one-quarter inch in diameter. When budding is to be done, take along only enough wood for half a day's work, leaving the rest safely stored. A piece of wood having a bud is prepared as shown in the illustrations "A" and "B" (next page). A T-shaped slot is made in the stock to receive the bud, a process called "shield budding." This is tied in place with either string, raffia or gummed tape, as shown in "C" and "D" (next page). The bud must be free to grow, and although it may be covered completely with wax, no part of the binding material should be close to it. Since it is not necessary to cut off all the tree in budding, enough of it may remain above the bud to brace the shoot that develops. Later, it may be necessary to cut back the tree to the bud so that a callus will form and cause the wound to heal properly.
Shield Budding.
Best results are obtained when a graft union is coated with melted beeswax. Another and cheaper wax may be made by combining four parts of rosin, one part of beeswax and one-sixteenth part of raw linseed oil. To this is sometimes added a little lampblack to color the mixture so that it can be seen on the graft. Again, care must be taken to prevent injuring the cells with wax that is too hot.
I have used many kinds of tying materials, but the one which gives me best results is gummed tape, which preparation I describe in another chapter. By wrapping it in spirals around a graft union, I have a material which holds the graft in place and at the same time excludes air. The rubber also seems to encourage the formation of that tissue which unites the stock and scion. In addition to tape, melted wax should be brushed into those crevices and cracks which always occur in making a graft.
It is usually advisable, although not necessary, to shade new grafts. To do this, cover them with light-colored or white paper sacks. Never use glassine alone for it causes the grafts to overheat and so destroys them. Whatever tying material is used, either to fasten on these bags or to support the grafts, it should be inspected at intervals during the summer, as it may constrict the graft or stock and injure or cut off the cambium.