ENCOURAGEMENT FROM FAILURES IN GRAFTING
Dr. G. A. Zimmerman, Piketown, Pa.
After improving from an illness of several years, and feeling tired, impatient and at times discouraged with progress in my physical condition, last spring I secured a few bunches of scion wood and turned to my old boyhood hobby for diversion; this time, however, by working on nut trees instead of fruit. In presenting the following at the request of others, I do not claim any originality, but simply draw the attention of interested parties to some possibilities and probabilities. My results have been very variable and many of them show as successful a failure as any one could possibly obtain. The scions referred to in the following tabulated record were put in from May 20th to July 20th and were well "mixed together" in the hope of giving better opportunity for cross pollenization, a few of every variety except the Hales being put in every day. The Hales were all put in late in July. I have grafted many other varieties of fruits and nuts but a record of the hickory only is shown below:
No. Growing Died % Growing % Died
Weiker 46 0 46 0 100 One graft to tree
5 3 2 60 40 T.W.T 1-1/4" diameter
5 1 4 20 80 U.W.T.
23 1 22 4.2 95.8 U.W.T.
Taylor 5 2 3 40 60 U.W.T. 10" diameter
27 7 20 25.9 74.1
Fairbanks 15 11 4 73.3 26.7
Vest 27 1 26 3.7 96.3
Manahan 22 7 15 31.8 68.2
7 0 7 0 100 U.W.T. 3" diameter
Laney 13 6 7 46.1 53.9
15 1 14 6.6 93.4 U.W.T. 6" diameter
Beaver 5 2 3 40 60 Scions poor. But one
grew 7 ft. 4 in.
Kentucky 19 7 12 36.8 67.2
10 1 9 10 90 U.W.T. 5" diameter
Kirtland 12 5 7 41.6 58.4
16 5 11 31.3 68.7 U.W.T. 5" diameter
7 1 6 14.2 85.8 U.W.T. Put on late
as also the Hales
Hales a 6 1 5 16.6 83.4 U.W.T. 3" diameter
b 35 0 35 0 100 U.W.T. 10" diameter
c 2 2 0 100 0 T.W.T. 1-1/2%" diameter
d 4 4 0 100 0 T.W.T. 2" diameter
e 3 3 0 100 0 T.W.T.
f 3 2 1 66.6 33.3 T.W.T.
g 6 4 2 66.6 33.3 T.W.T.
—— — —- ——- ——-
Total 338 75 263 22.2 77.8
The last two series of the Hales made 100% start also but bugs
killed three grafts.
U. W. T. means a tree from which all the lower limbs were cut back
to about a foot or eighteen inches and grafted, a few top limbs
having been left intact.
T. W. T. means a tree from which the top had been cut, the lower limbs and stub having been grafted, although a few of the lower limbs were not sawed off.
A study of the above record is interesting. All of my stocks are of the mockernut type, varying from three-fourths to two inches in diameter, except a few trees to which I refer specially as T.W.T. and U.W.T. It will be noted that the Weiker and the Vest made the poorest catches. It could not have been due entirely to weather conditions or the condition of the scions, for the scions of these two varieties were equal to anything I had. In view of the fact that they are both very desirable nuts, I always carried a few scions and kept placing them frequently as I placed other varieties. Many Vests were placed at the same time as the Fairbanks, which shows 73.3% catches. The one Vest that did catch, however, made a very thrifty growth, showing that it is possible apparently to do well on the mockernut.
With the Weiker, about the 15th of July, I put five scions on the limbs and trunk of a tree about 1-1/4 inches in diameter, the top having been cut out, with three catches, 60%, against another lot of 46 with 100% failure and 23 more with 4.2% success. Such antics are difficult to understand.
Many of the scions were put in the trunks of the trees; others were put on the small branches with the splice graft. The scions placed on the trunks, or the larger limbs near the trunk, apparently did somewhat better than the splice grafts further out on the limbs. In the walnut and other sappy trees, however, the splice graft out on the small limbs did better.
It is of peculiar interest that all of the large trees from which the lower limbs were sawed and the stubs grafted, the topmost limbs having been left, designated as U.W.T., did badly. While in the case of the five Hales, three had 100% and two had 66.6% catches. These two also had 100% catches but bugs ate the tender shoots and killed three of them. These trees had the tops cut off last fall leaving only a few lower limbs. They were put in on July 20th after the sprouts had well started on the trees. The sprouts were not taken off but their tops were pinched out. These grafts made a growth of from one to two feet or more. At the same time a tree was trimmed (Hales b in the record) and all the lower limbs grafted with Hales, leaving a few top branches only. Thirty-five were set and not a single one grew. The location of this tree was better than any of the five above referred to, because a couple of those trees were standing on the top of a rock where one would wonder how they could exist, and it was so hot when I placed the grafts that I had to quit and get out of the sun. In spite of that 100% grew.
A study of the above record leads to the conclusion that there is very little difference in plant and animal cells and it seems clear that certain old, underlying principles must be dealt with. I need not refer to heredity because, while it is undoubtedly quite possible, perhaps, to influence heredity tendencies so as to get stocks to accept scions more readily, it is not the major issue for most of us just now. Next spring we will take what heredity has given us and be satisfied. However, it appears certain that our results in grafting the various stocks we now have will depend largely on our ability to:
1. Regulate plant circulation. 2. Stimulate cellular activity to a point compatible with wound repair, defensive and growing processes. 3. Control plant cell nutrition.
One of the very first things we physicians do upon seeing a patient is to investigate his circulation. If the pressure is too low or too high, for any reason, we immediately take measures to correct it, because we know that disastrous results will quickly follow if that is not looked after. Plant circulation, or sap flow, is no less important. Mr. Riehl, Mr. Jones and Dr. Morris made great strides when they advanced the ideas of covering the wound and the scion completely to prevent evaporation, thereby also controlling the sap pressure. With the exception of shading, pruning and defoliating, this is about the only method we have of preventing evaporation. Defoliation, of course, interferes with the tree's power of growth. Controlling the humidity is probably not practical on a large scale.
A proper and careful cutting of the tree beforehand is important. It appears that to cut the top completely out while the tree is dormant, so disrupts the routine circulation that the few lower branches which are left intact, are well taken care of and, it seems to me, that this, together with the stimulation of WOUND REPAIR by cutting and allowing time enough for the cells to get into action, was the prime reason for the 100% success in the three Hales and the cause of the 100% failure in the other Hales tree.
Other methods of controlling the circulation are of course drainage, irrigation, mulching, location of the orchard, placing of condensers of moisture, such as stones and other hard substances beneath the trees, and many other contrivances which are in use, and which I shall not discuss.
With reference to stimulation of cellular activity we are considerably concerned. In medicine I have found the subject of wound repair and immunity most interesting, the two subjects seeming to be more or less related. Some animals will repair wounds and immunize readily, while others will not. In a general way young healthy animals and human beings immunize most readily, while older ones frequently fail almost entirely. Interestingly enough plants seem to be strangely similar in this respect, and the thing that stimulates cellular activity for defensive purposes (immunity) apparently stimulates growth and wound repair. The thing that stimulates most actively for a special purpose is the thing itself, the best stimulant for wound repair being the simple injury. To illustrate briefly: In my work last summer I came in contact with two enemies, yellow jackets and copperheads. The copperhead stimulated me to carry a club in defense, while for the yellow jacket the club was of little value and I rather preferred carbon bisulphide. Had I ignored my senses and allowed nature full sway, as a tree does, the snake would have injected his venom and the yellow jacket his toxin, and my cells would have accepted their only alternative and proceeded at once to build up a specific defense, after which they would have been in better shape for development, providing the poison would not have been so great as to prove fatal. Injury to a tree certainly does stimulate wound repair, defense and growth. It is well known that trees with many transplantings, root injuries, transplant much more readily, and the nurserymen use this method of stimulation as a routine procedure. I learn in Florida that in order to transplant a good size palmetto, they are in the habit of digging down on one side and cutting the roots the year before removal. It will then transplant more readily. Pruning has the same cell stimulating effect if done at a time that will retain the stored nutrition. An attack of disease just as surely stimulates cellular activity and growth but it is too frequently followed by disaster.
We have all heard of driving rusty nails into trees (thinking the iron produced the beneficial results), cutting a slit in the bark of the limbs and trunk for "bark bound" so called, etc., all of which have stimulating effects with more or less permanent injury to the tree. Who knows but what the sap sucker, with his ability to dig into the bark and extract a piece of cambium, was not sent to us to aid in preserving our trees by stimulating new growth?
In my work last summer trees that were subjected to slight injury before hand apparently accepted a larger proportion of grafts. I will briefly cite two specific illustrations. A little butternut tree located near the house was the object of my efforts for over two years. During my illness I frequently went out and pruned a few branches or put on a few buds. Something would happen to me and possibly I would not see it again for months, and in the meantime the buds would be strangled or knocked off. Another little hickory tree stood in the roadway. Harrows, plows, wagons and even logs were dragged over it. Grafts on both these trees caught rather readily last spring. In fact two black walnut grafts on this little butternut were two of the very few that I got to grow at all last year. My walnut grafting was almost a total failure. I have this to say, however, that I had no dormant walnut scions, my scions all being cut in May or June.
Mr. Jones, by marking the site of his patch bud several days in advance, admirably carries out this idea by locally stimulating the cambium cells. Dr. Morris's scheme of using white wax, besides regulating sap pressure, allows the actinic rays of the sun to stimulate cellular activity. Cutting the top out of the tree, which disrupts the normal circulation and throws it into the few lower limbs, besides stimulating the cells into activity, has apparently in a large measure accounted for the slight success that I have had. Other methods such as injecting some substance under the bark, applying antiseptics, or some stimulating chemical in a similar way, as "Scarlet Red" is used in skin grafting to increase epithelial growth, may aid materially. Certain chemicals applied to the tree and leaves, as used in sprays, seems sometimes to stimulate growth in a way that can hardly always be accounted for by the checking of the disease for which it was placed.
Much more could be written on cellular stimulation but enough has been said to encourage others to make observation in this connection, for it is highly probable that the lack of proper stimulation of the cambium accounts for more failures in top working trees than we are aware of.