Growing Nuts in the North Part 9

Although bud wood may be stored in any of the three ways mentioned, it should not be waxed. Because of this, it is more likely to deteriorate.

It must be examined frequently and if mold is found, the wood should be dipped in a Bordeaux solution. After drying, it may be placed in storage again. It is a good plan to wrap bud wood in tar or asphalt paper when storing it. However, I have found that the best storage conditions for all scionwood that I have yet discovered is in the use of peat moss.

Peat moss must be on the distinctly acid side in order to perform the function of storing scionwood. Most peat moss is generally acid; however the simple litmus paper test with which every high school pupil is familiar, can be made. Having acquired good acid peat moss, dampen a sufficient quant.i.ty to pack the scions in to give them liberal protection. Do not make the bundles of scionwood too large, from 10 to 20 scions in a bundle is better than a large number and much easier to handle. The moss should be prepared exactly the same as advised in storing chestnuts (see chapter for storing seeds). In this case it is not necessary to wax the scions at all. The moss should be applied by sifting it into the open s.p.a.ces between the scions and a larger wad at the base of the cuttings, not at the terminal or bud ends as these would be better left unpacked. The package is now rolled into a cylinder, using tar paper or asphalt treated paper, and both ends left open. Do not use ordinary paper or wax paper as it will turn moldy. Cylinders of tar paper containing the packed scions should be placed in a damp room like a cellar with a dirt floor which is cold enough to keep potatoes and other roots in good condition throughout the winter. If the cellar is not a good storage cellar for roots and herbs it will not be good enough for the scionwood as it will be too warm generally. Neither should they be frozen solid, therefore if a good root cellar is not obtainable then these should be put in the Harrington graft box already described or placed under the sawdust in an icehouse and close to the ice. An old-fashioned ice refrigerator will also make a good storage bin, placing them close to the ice at all times.

[Ill.u.s.tration: Drwg by Wm. Kuehn. _Making a scarf with a plane preparatory to grafting._]

Selection of good scionwood and bud wood, a very important matter, is made according to definite standards. Some plants graft better if wood is used that has two seasons' growth, but, in general, wood of the current season's growth is used. It must have reached its maximum possible maturity before it is cut. Also, some attention should be paid to the vigor of the growth which it has made during the season. For instance, in choosing between wood which has made only two or three inches' growth and that which has made a foot or more of growth, both being equally sound and mature, the more vigorous should be chosen.

Attention should be paid to the development of the buds, which should be plump and never immature.

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 pa.s.s 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, bra.s.s 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 sc.r.a.ped 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. Ill.u.s.trations 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 ill.u.s.trations "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.

[Ill.u.s.tration: Drwg by Wm. Kuehn _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 gla.s.sine 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.

After a scion begins to grow, it must be firmly braced against the force of the wind, for a heavy gale can rip out grafts made years before.

Laths make good braces for growing shoots. They may be attached to the main branch by stout waterproof twine such as binder twine, and the growing graft tied with soft muslin strips to the lath. As the graft grows more muslin strips should be used to keep the excessive growth anch.o.r.ed to the lath. Grafts will often make three or more feet in growth in one season.

It is important to remember that sprouts or buds which start from the stock must be rubbed off. If they are allowed to flourish, they may prevent the scion from growing. When working over a tree several inches in diameter, it becomes an art to keep the tree stock satisfied, yet to encourage the growth of the scions. In large trees, a few sprouts must grow to nourish the root system, but this is not necessary if the stock is one inch, or less, in diameter.

Chapter 17

GRAFTING TAPE VERSUS RAFFIA

It is necessary that a person who is grafting trees and developing hybrids experiment not only with the plants he is interested in, but also with the equipment and materials he uses. For more than twelve years, I used raffia to tie the grafts I made, becoming more annoyed and irritated with its limitations each year. Finally, I began trying other materials, until I found one which I think is very satisfactory. This is a rubberized grafting tape.

At my nursery, we make our own tape. We buy pure rubber gum, known as Lotol NC-356, from the Naugatuck Chemical Company, at a cost of $7.50 for five gallons, F.O.B. their factory. With this, we use unbleached muslin of an 80 x 80 mesh, or finer. As the muslin is usually a yard wide, we fold it and take it to a printing firm, where, for a small charge, it is cut into both one-half and three-quarter inch strips by being fed through a paper-cutting machine. We use the wider strips for heavy work on large trees which have three to five-inch stubs; the narrower strips we use in the nursery, grafting young seedlings.

First, pour about a gallon of the rubber compound into a twelve or sixteen-quart pail having a smooth, rolled edge. Next, separate a dozen or so of the strips of muslin. Then, set out a pair of rails on which to dry the tape after it has been dipped. I make these rails by using two 1" x 2" boards about twelve feet in length, nailed together at the ends with boards two feet long. This frame, resting on carpenter's horses or benches, makes a good drying rack.

Holding a piece of tape by one end, submerge it in the rubber solution, forcing it down with a spatula or knife. Swishing it around or moving it up and down several times helps to fill the pores with rubber. Drag it from the solution by pulling it sharply over the rolled edge of the pail, using the spatula on the upper side of the strip to sc.r.a.pe off superfluous rubber. A little practice soon enables one to judge the amount of rubber needed on the tape. There should not be so much that it drips off. Hang the tape on the rack so that the ends are attached to the rails, the tape sagging slightly in the center. s.p.a.ce the pieces of tape so that they do not touch, for, if they do, they will be very difficult to separate later. After they have dried for twenty-four hours, wind the tape on pieces of cardboard about one foot square, being careful not to overlap the tape. The tape is now ready for field-work.

I want to mention some of the advantages I have found in using this rubberized tape rather than raffia. The tape is uniform throughout and is stronger than raffia. It does not fly around and frequently get tangled as the latter does. There is no necessity for keeping it slightly damp to be usable. It may easily be torn off at any convenient length or it may be cut without injuring the edge of the grafting knife.

A last advantage is that it is self-sealing since it overlaps on itself slightly when wound around a graft union. Because of this, there is no necessity for painting the finished graft with melted wax as is absolutely vital when using raffia. Personally, I use wax in addition to the tape for I feel that it is probably safer with that extra protection. Also it gives me an opportunity to wax over the tip end of the scion when it is devoid of a terminal bud.

The only disadvantage in using tape is its cost which, I must admit, is very much higher than that of raffia. But if, by using tape, twice as many grafts can be made each day, and if the resulting takes are 50% better, as they have been in my experience, then the cost is justified and raffia is actually the more expensive to use.

Chapter 18

EFFECTS OF GRAFTING ON UNLIKE STOCKS

It is unquestionably a great shock to a tree when 90% of its top is cut off. If it is healthy and vigorous, the root system will try to recover, using every means possible to do so. If a new top is grafted to it, the stock must either accept and nourish that foreign and sometimes incompatible new part, or give up its struggle for life. Nature and the tree stock usually accept the challenge and the graft begins to grow. In an attempt to continue with its own ident.i.ty, the stock will bring into activity advent.i.tious buds. These are tiny microscopic buds imbedded in the bark of a tree that are not apparent to the eye but are nature's protection against destruction of the individual plant. But these must be removed by the horticulturist to insure proper nourishment of the grafts.

Because the root system is striving hard to live, and because it is usually the stronger, it may force the top to accept certain of its characteristics. Occasionally, it may a.s.sume some qualities of the original top. Such cooperation is necessary if either is to survive.

First of all, the grafted scions must accept the vital quality of climatic hardiness, a powerful factor developed through ages spent in a certain climate. To hasten the acclimatization of a tender variety, I cut scionwood from such unions early in the winter, storing it until spring. When these scions are grafted on new root systems, I find that they are much more readily accepted than the first grafts were. The following season, I allow the grafts of this later union to go through their first winter of exposure. Early each spring I continue to cut scions from the most recent unions and graft them to new root systems, so hastening and setting the factor of hardiness through frequent as.e.xual propagation.

Because my observations of the effects of scion on root and vice versa, have not extended over a sufficient period of time, I think it is possible that the changes I have seen may be only transient. In any case, I do know that the phenomenon occurs, for I have seen many examples of it.

One instance in which the stock was apparently affecting the scions, occurred in the case of several varieties of black walnuts which had been grafted on wild b.u.t.ternut stock over a period of sixteen years. The walnut top flourished but tended to outgrow the b.u.t.ternut, so that the caliber of the walnut was greater than that of the stock a few inches below the graft union. I also noticed that, although the graft began to bear about as early as black walnuts do when they are grafted on their own species, the nuts did not mature at all during the first few years of bearing. In 1938, after a favorable season, I found mature nuts on one variety, the Thomas. These nuts varied in size more than they do when grafted on black walnut. The most surprising thing about them, though, was that they did not have the characteristic black walnut flavor. When properly dried and cured, they could have pa.s.sed as an entirely different nut since they tasted like neither the black walnut, the b.u.t.ternut nor the Persian walnut.

The overgrowth of the Ohio black walnut, grafted on b.u.t.ternut, was even more apparent than that of the Thomas. These nuts were, as I have said, immature the first few years they appeared and they, too, lacked the usual black walnut flavor. In their case, however, the most striking change was in the shape and structure of their sh.e.l.ls which were elongated like b.u.t.ternuts, with corrugations typical of those found on b.u.t.ternuts and nearly as deep and sharp. (See Ill.u.s.tration in Chapter 1, Page 5.)

In 1937, I made experimental graftings on native black walnut stocks of the Weschcke No. 4 b.u.t.ternut, a variety I found to be superior to hundreds of other native trees tested. The grafts grew luxuriantly and in 1940, produced about two pounds of nuts. These nuts were approximately 30% larger than those on the parent tree. They cracked well and the kernels were similar to those from the parent tree. They definitely distinguished themselves, however, by being a free-hulling nut, which is not true of the mother tree nor of most b.u.t.ternuts. Soon after the nuts had dropped to the ground and were still green, they were hulled and their hulls peeled off like those of the Persian walnut, leaving the nuts clean and free from remnants. Apparently this phenomenon was a transient one since later crops did not display this free-hulling feature.

I have mentioned, elsewhere, the seedling apricot which came into bearing in St. Paul, and how I obtained grafts before it died during a very cold winter. I have grafted scions of this apricot on both hybrid and wild plum stocks repeatedly and this apricot now exhibits a material gain in hardiness. It overgrows the plum stock, but this does not seem to inhibit its bearing, the fruit growing to greater size than that of the mother tree.

These are some of the instances in which I have seen stock exert a definite, and, mainly a beneficial influence on its grafted top. It may easily be that these are only of a temporary nature and until I have seen them maintained for many more years, I must consider them to be transient effects.

Chapter 19

DISTINGUISHING CHARACTERISTICS OF SCIONS

Loss of identification markings from my grafted trees has, on occasion, caused me much confusion. There was one time when I had from six to ten varieties of hickories and their hybrids grafted on wild bitternut hickory stocks, totally lacking in identification. Although this disconcerted me considerably, I knew of nothing I could do except to wait for the grafts to bear nuts and determine the varieties from these.

As I continued my experimental grafting, I made sure that the tags I used were not only indestructible, but also secured to the grafts in such a way that the action of the wind could not wear them out nor cause them to drop off.

Not long after this had happened, I received from Dr. Deming a shipment of about twenty varieties of hickory scions. While I was preparing this material for grafting, I noticed that each variety could be readily distinguished by its appearance in general and, specifically, by differences in its leaf scars. I also noticed markings on the bark, particularly the stomata, which differed with each variety. Color and stripes added further differentiation. Although I also found variations in the size and shape of the buds, I later discovered that these do not always remain constant within a variety, but depend somewhat on each season's growth. For instance, a second growth sometimes develops during a favorable season with a large number of lateral buds growing out of it like spines.

It seemed to me that if scions could be maintained in an approximately fresh state, they would furnish a key by which any variety of graft could be determined as easily as it could by its nuts. I therefore set myself to preserve scionwood in its fresh state. First, I cut five-inch pieces of plump, healthy wood, each piece having a terminal bud. I placed these buds downward in large test tubes which I then filled with pure, strained honey. Such models did very well for a time, but after about a year, the honey crystallized and of course the scions were no longer visible. I emptied the tubes and washed them, cleaned the scions in warm water, replaced them and refilled the tubes with pure glycerine.

I submerged a thin, zinc tag, stencilled with the varietal name and bent to conform with the contour of the tube, inside of each one as a name plate which could not easily be lost or removed. I also labeled each cork with the name of the variety enclosed so that any one of them could be located when looking down at a nest of tubes in a vertical position.

In order to display these preserved specimens at ill.u.s.trated lectures, I had a rack made of redwood, of a size to hold twenty tubes. The tubes could easily be taken from the rack for closer observation by members of an audience. I find this to be an interesting adjunct to various nut culture exhibits I make in trying to promote nut culture education.

Since I was able to identify my unlabeled, hickory grafts by means of this catalogue of submerged scions, I consider it of great practical worth. At the present time, I have about 50 hickory specimens, a good catalogue, although not a complete one. I see no reason why the same thing could not be done with black walnut or any other kind of nut scions.