TOP WORKING HICKORIES

Robert T. Morris, New York

At the present time when our views on the subject of top working trees are based upon incomplete knowledge and experience perhaps it is unwise to present a paper upon the subject which might be taken as authoritative. On the other hand my experience to date is worth recording for its face value, subject to change of view subsequently.

Different species of hickory act differently when subjected to top working methods. The bitternut may be cut back severely without giving evidence of any great degree of shock. The shagbark on the contrary makes slow recovery and many years are required for a cut-back shagbark hickory to regain normal equilibrium between top and root. The pignut and mockernut apparently stand midway between the bitternut and the shagbark in respect to the trimming of the top. My experience with shagbark includes the top working of trees ranging from a few inches in diameter up to fifteen or twenty inches in diameter, and the cutting back has included all stages from actual felling of the tree to cutting off half of the top or less than half of the top. The idea of felling trees completely was to graft stump sprouts or to insert the slot bark graft into the stump near the ground. When this has been done the larger hickories do not send up stump sprouts at all and the root dies excepting in cases in which a slot bark graft has been introduced. The graft grows slowly without a great degree of vigor and requires so many years for balancing the root that the method has not been practical up to the present time. The same statement is true of the shagbark hickory which has been trimmed back very severely leaving nothing but the stubs of large branches to be grafted immediately or for the purpose of grafting sprouts in the following year. The bark of the shagbark hickory is so hard that new shoots are choked severely and many years are required before they have a secure hold upon the stock. My final conclusion is that we may cut shagbark limbs having a diameter of three inches or less for the purpose of leaving grafting stubs. If a large number of grafts are inserted in such a topworked tree or in stock sprouts which start and are grafted in the following year the work is successful. In order to avoid the labor of topworking a large shagbark tree in its entirety we may graft only one or two limbs and allow stock sprouts to grow on other limbs until both stock sprouts and graft sprouts have become well branched. Branches carrying stock sprouts may then be removed a few at a time year after year, leaving the graft sprouts in charge finally.

By means of the bark slot method of grafting grafts may be inserted in any part of a hickory tree. The bark slot method consists in using a chisel and mallet for cutting parallel lines the width of the scion in the bark of the stock. The tongue of bark between the parallel lines is pried outward with the point of the chisel until the scion has been inserted next the wood and the tongue of bark is then allowed to return to place, leaving the scion interposed between the tongue of bark and the wood. Rules which apply to the shagbark may be applied to all of the hickories with which I have experimented. When cutting back the limbs in preparation for topworking it is well to leave as many as possible of stubs or branches of small diameter. Branches of small diameter may be grafted by ordinary cleft grafting methods but branches of larger diameter should be treated by the bark slot method. At the present time and in the locality of my country place at Stamford, Connecticut, melted paraffin suffices in place of grafting wax and melted paraffin is brushed over the entire scion, buds and all, as well as over the wound in the stock.

The time for cutting back hickories in preparation for topworking is probably important and in my experience to date, autumn cutting is preferable. The reason is that a good deal of activity is going on in the tree before it enters into a state of winter rest and wounds are pretty well repaired. In winter cutting there is some danger of incomplete repair and in the springtime the free flow of sap invites the entrance of various enemies, bacterial and fungous. Summer cutting according to the laws of plant physiology would cause more shock to the tree than cutting at any other time, although practically I have done this successfully. Without regard to season for cutting in preparation for topworking it is very important to trim cut ends very smoothly with a sharp knife in order to remove ragged tissue left by the saw. It is difficult to persuade employees to do this and it will not be done as a rule unless the owner looks after the matter personally. The smoothly trimmed end of the cut branch should immediately be protected with white paint, melted paraffin, or some other protective covering.

What are the disadvantages of the slot bark method of topworking hickories? The scion does not have such a secure hold upon the stock as it does in cleft grafting and it will blow out in a high wind unless it is protected by braces. I have found it not harmful to a tree to fasten laths to the stock for holding the growing scion, driving galvanized iron nails through the lath directly into the stock. Unless growing grafts are well braced by some method the entire season's work may be lost in two minutes of a gale preceding a thunderstorm in summer. By the slot bark method, in other words, we may catch more grafts and lose more grafts than by any other method with which I am familiar, but the loss may be avoided by proper attention.

The best time for grafting varies with the locality. At Stamford I have grafted hickories from February until September. Very early grafting is largely a failure because of incomplete repair of the wound in the stock and scion. Late summer grafting is not practical because the scions which make a start do not lignify their new shoots sufficiently to withstand the winter cold. In late April or early May when the sap is running very freely we also have a considerable loss of scions because an excess of water causes the scion shoots to grow too rapidly before wound repair has taken place to the point necessary for conducting nutrition for the growing shoots. Grafting after the leaves are pretty well out on the tree has given me best success. Grafting from then up to the last week in July has been found to be practical. Scions for topworking hickories have been employed for what I call "mediate" and "immediate" grafting. By mediate grafting is meant the employment of scions which have been cut while they were dormant and which have been stored in any appropriate way. Immediate grafting means the transference of scions cut from one tree and used upon another in the same hour or day. Mediate grafting is the sort which belongs to all history of the subject and immediate grafting relates more particularly to my recent experimental work.

Mr. Bechtel: What kind of wax did you use if any besides paraffin?

Dr. Morris: I have given up everything but that. The paraffin has a number of special advantages. In the first place, it seals any wound against infection from bacteria or fungi. It prevents moisture from rain carrying bacteria into the wound. It prevents evaporation from the cut surfaces.

Mr. Bechtel: Doesn't it melt too much in the sun?

Dr. Morris: It might with you and you might need to use a harder paraffin. There are a great many kinds of paraffin. The paraffin series is a large one in chemistry. The one I find best for our locality is the common parowax that you can find in any grocery store. I use just the pure straight thing but in your country you are further south and may need a different one. It does melt some in the middle of a hot day and will be nearly fluid sometimes but it hardens up when the sun goes down.

Mr. Foster: Were the grafts kept in cold storage?

Dr. Morris: I have used two ways of keeping grafts for top working. Some have been kept in cold storage, others have been kept in the ice house. I have been in the habit of kicking up the sawdust and dropping scions in the hole not very far above the ice. Last year I could not get any ice and two years ago I could not get any but the scions kept just as well in the sawdust near the ground. Then I have kept them packed in leaves with two feet of leaves on top of the scions. I have also kept some as Mr. Jones has but the difficulty is in keeping them at the right degree of moisture. The enzymes go to work the minute the cells of the scion have a full charge of water despite low temperature unless it is actually below freezing. Scions of another kind are the ones that I cut off from one tree and put on the next tree the same hour or day. That has only been possible by this method that I now employ. Almost any time in the summer we can do that without keeping the scions in storage at all. I gave some of them a resting period experimentally for a day or two but to no advantage.

Prof. Close: Don't you have to be pretty careful with the melted paraffin so as not to injure the tissue?

Dr. Morris: Yes we need special apparatus. I took a lantern, cut out the top and sunk a spun cup down in the lantern. On a cold day I turn the alcohol flame higher than in a warm day. I have been trying to have this lantern made so that it could be got on the market. There is nothing else to my knowledge that will allow the grafter to regulate the temperature of melted wax according to the weather. I am going to get it manufactured so you can each have one.

Mr. Bixby: There is a series of paraffines pure paraffines which are known only in chemical laboratories and also a number which can be obtained without much difficulty. The common parowax I think is the grade that is known in the trade as 120. That is it melts at 120 degrees F. but paraffin can be obtained without much difficulty that melts at 125°, 128° and 130°, so if the parowax is too soft for Mr. Bechtel's district I am sure he can get something that will be all right. He might have to send to New York to get it but it is readily obtained there.

Mr. Bechtel: I have used bees wax and find that that melts at a higher temperature.

Dr. Morris: I want complete transparency.

Mr. Foster: Would it be out of order for a beginner to ask what type of grafting Dr. Morris uses in his work on these trees.

Dr. Morris: I think that somebody who was not a beginner might ask that quite as well. I have tried almost all the methods employed by the experts and have gotten down to very simple principles. If I am going to get fifty, sixty, eighty or ninety per cent of catches in hickory as we sometimes do I have to use methods that are very simple. For limbs that are small not larger than one's finger the plain cleft graft is good enough and I like as far as possible to choose a branch that is about the diameter of the scion. If the limb is larger in diameter than the scion I make my cleft to one side so that the cambium line of stock and scion will correspond. It is important to have cambium layers together. By all means the best feature of all in my grafting work is what I call the bark slot. This bark slot consists in making two parallel lines in the stock bark the width of the scion. I turn down that tongue of bark and stick in the scion. I turn back the bark again and bind all with raffia. That is the bark slot graft. The bark slot is by all means the most successful method that I have ever employed. What are the objections to it? Not so firm a hold on the stock as you will get in a cleft. What are you going to do about it? Put on good strong braces for the growing stock. I find it does not do much harm to drive galvanized nails right into the tree to hold the brace, three or four nails right into the limb, and then tie the rapidly growing shoot to the brace. If I do not do that the new shoot blows out very readily when I use the bark slot. In other words you will catch more by this method and lose more unless you give the grafts a good deal of attention.

Prof. Close: How do you trim the scion?

Dr. Morris: I trim it mostly with one good long cut on one side and sometimes turn it over and make a little nick on the other, but one good long cut is usually all that it needs.

Prof. Close: Supposing the bark does not peel?

Dr. Morris: If it does not I think the chances are against its catching your graft. I have done all my grafting until this year at times when the bark peeled but this year I carried it up into September after the bark had set and I am trying to see if I can get a catch then. In that case I take a chisel and chisel off the bark where it is hide-bound. The experiment may be a failure but I have had so many failures that they are sort of a pleasant experience.

Mr. Foster: In the cutting back I understand that you prefer to do so when the tree is dormant. Then in the spring when you start your grafting do you leave that cut just as it is or do you cut it off again?

Dr. Morris: These are very important questions that are coming out. When you have sawed off the limb trim the end neatly with a sharp knife. An employee will almost always leave the cut end ragged but if you do it yourself and have smooth ends and cover them with paraffin you can graft right squarely on that end. Turn down your bark for a slot and stick in the scion at any time. If the cut end was made by someone who was not careful make a cut down through any living bark with a chisel or a knife until you get down to the wood, then make parallel lines from that point and turn down the tongue of bark. I have put in scions where I had to use a heavy chisel and mallet to turn down the tongue. It was not necessary to put on any binding there where the tongue of bark was so thick.

Prof. Close: I understand you to say that if the end has become dried you go down below the dried part?

Dr. Morris: When I find the end of the stub dry I go below that point to get live bark for grafting purposes. After my scion is well under way a year or so then I saw off any projecting stub beyond the graft and put paraffin over the cut end. That form of graft works very well except that it makes more work.

Mr. Littlepage: I have been very much interested in what Dr. Morris said. I found it no trouble whatever to get a hickory from four to six or eight inches to grow a great big graft, but I have never seen one live three years. I have my woods full of dead ones. I have one in front of my house now which I slip-bark grafted about the diameter of two inches and it is still growing but I expect an invitation to its funeral next spring. I have never seen a hickory tree successfully grafted over five inches in diameter. I found in my woods that the trees would sometimes die down to the ground. If they lived they would drag along for two or three years. If those of you who were out there yesterday had had a little more time I could have shown you those dead hickories. I would like to know what your experience is in grafting hickories over an inch in diameter.

Dr. Morris: That is an important point and it relates to the matter of cutting back to such an extent that it causes too much shock to the tree. In very large hickories I have cut them hack to short stubs and have had a number of them die. On the other hand where I have cut back so that the largest limbs cut were not more than three inches in diameter those trees would do very well. I have living shag bark grafts now on trees that are from five inches to more than fifteen inches in diameter.

Mr. Littlepage: Do you cut these back in the winter or spring?

Dr. Morris: I do not remember about all. Some, were cut back in both seasons. Winter is probably better. Autumn better yet.

Mr. Littlepage: I cut mine in the spring.

Dr. Morris: That has a lot to do with it if the trees bleed too much.

Mr. Foster: Are your pignuts native?

Mr. Littlepage: I think most of them are worse than that.

Mr. Foster: They are familiarly known in my state as pig nuts.

Prof. Close: You could top-work them.

The President: We will proceed with the next number. We are honored in having with us the President of the National Nut Growers Association who has come to us all the way from the southland to tell us about selection and propagation for the improvement of the pecan. I now have the honor of presenting to you Mr. Theodore Bechtel, President of the National Association.

Mr. Bechtel: Mr. President, Ladies and Gentlemen: After having listened to so many good papers and addresses it seems to me that as far as imparting any knowledge to this audience my trip may have been in vain. However I assure you as this is my first visit to Washington it lacks a whole lot of being in vain from what I have already seen and enjoyed. I may be able to add a few points to what has already been said.