Part 11

MR. STOKE: I mostly use a plain splice. The cut is about four times as long as scion diameter, if it is on a stock of the same size. It is the best method. I use also a modified cleft graft with a little trimming. Mr. Jones brought out that modified cleft graft and I have made a little change. Here is the stock, and a modified cleft graft is a side graft with the stock top cut off. You cut in at an angle far enough and you put your scion in here and there is your modified cleft graft. You get contact on all four lines. It takes experience and judgment. You cut your scion wedge and then make your understock cut and you will seldom make a mistake after you get experience. That is a side graft and a modified cleft graft. That makes a flexible portion here and you get a fit on both sides. But with the ordinary cleft graft, if you go to the end of your stock you still have a split and not a perfect fit.

MEMBER: Would you explain that? If your scion is not the same size it might over lap or ... how do you handle that?

MR. STOKE: If the scion is undersized, you don't cut so deep. Sometimes the stock is a little oversize. You simply cut less deep in your stock. If you have a large stock and small scion I'd make a bark graft.

MEMBER: I should like to bring up one point. That is produce more nut trees and do it cheaper. It seems to lie between Mr. Gerardi and Mr. Bernath. Mr. Gerardi can set between six and seven hundred per day, and tie them himself, and Mr. Bernath will graft between seven hundred and a thousand a day with someone else doing the tying.

MR. CHASE: We have tried all these grafting methods with varying degrees of success. Our propagation experiments at Norris have been directed at the development of more economic methods.

Conifer grafts are often placed in a grafting case for rapid callusing. This year we tried some black walnut grafts and found that they callused in 10 to 14 days when placed in a grafting case. These were bench grafted on piece roots, using modified cleft and side grafts. Later we tried chestnut with excellent results. Then we made more chestnut grafts, wrapped them in damp moss and placed them in a lab oven with a temperature of approximately 75 degrees. These callused rapidly and were planted immediately in the nursery. They made good growth.

We think that some adaptation of this method has possibilities in our region. Often our chestnut grafts are damaged by late spring frosts. If we can bench graft, callus, and then hold the grafts until favorable weather, frost damage will be eliminated. It may be possible to handle black walnut in some similar fashion. Then we would be dealing only with successful grafts. A cold frame provided with heating cable should be adequate.

Factors Affecting Nut Tree Propagation

F. L. O'ROURKE, _Department of Horticulture, Michigan State College_

Propagation of nut trees is primarily involved with the problems affecting the perpetuation of selected clones by vegetative means. It has been indicated by Morris (14), Reed (18), and others that trees produced from seed are of inferior value for nut production. Seed propagation, however, must be practiced to produce the necessary rootstocks upon which the selected varieties are budded or grafted.

Seed Propagation

Barton (1) indicated that while some few seedlings may be produced without prior seed stratification, after-ripening of the seed for 2 to 4 months at 35° to 50° F. markedly increased seedling production with hickory and walnut. Chase (4) found that black walnut seed sown in November yielded more and larger seedlings than when planted at a later date. Chase (5) also reported that nuts containing larger kernels produced larger seedlings, and that planting 1 to 2 inches beneath the surface yielded larger seedlings than deeper placement. There have apparently been little or no observations made on the performance of seedlings for rootstock purposes between different parental strains except for Chinese chestnut as reported by McKay (12).

Clonal Rootstock Propagation

The difficulty of propagating any selection of nut trees by vegetative means has discouraged selections for rootstock purposes. Only filberts offer such an opportunity for selection on somewhat the same basis as the East Malling clones of apple rootstocks which produce different sized scion varieties after grafting. Unfortunately, no non-suckering desirable clones of filberts have yet been reported and even the non-suckering Turkish tree hazel is grown from seed when such rootstocks are used (16).

Propagation by Cuttings

Gellatly (7) quoted the success of the East Malling Research Station in England in rooting cuttings of walnuts grown in the greenhouse and reported on his own experience in producing short roots on dormant cuttings of heartnut and Persian walnut. The writer (15) has occasionally produced roots on softwood cuttings of pecan and hickory set in a mist humidified greenhouse but the cuttings did not survive. Mist humidification has been a distinct aid in retaining foliage on softwood cuttings of filbert and Chinese chestnut until roots were formed but unless the axillary buds were developed sufficiently to make new growth immediately thereafter, little or no survival was secured. Apparently when the cuttings were succulent enough to form roots the buds were too immature to put out new shoots. If one waited until the buds were developed the tissue at the base of the cutting was too highly lignified for root formation. The use of synthetic plant hormones on cuttings of nut-tree species has been of questionable value.

Propagation by Layers

Mound layers are used quite successfully for the propagation of filbert varieties but have not proven of value with other nut-tree species. Chinese chestnut has been reported to layer easily but experiments with both mound and trench layers of selected varieties of this species at the Glenn Dale, Maryland Station of the U.S. Department of Agriculture gave negative results. The writer (15) has occasionally rooted pecan, hickory, and Chinese chestnut by aerial layering. A marcot box containing sphagnum moss kept moist by a glass wick immersed in water from a bottle at the lower end was employed. The time and labor involved were so great that the experiments were discontinued.

Propagation by Grafting

Bench grafting of walnuts and hickories has been adequately described by Bernath (3), Hardy (8), Lounsberry (10), Slate (24), and others. This method has been tested on a commercial basis and apparently should be considered as one of the most efficient ways to produce nut trees quickly and cheaply in large quantities. Greenhouse and storage facilities are required and keen expert attention must be given the newly-made grafts to assure success.

Reports on top-working and field grafting are both numerous and voluminous. Morris (13), MacDaniels (11), Wilkinson (29), and others have demonstrated the value of cutting back the stock a week or more before setting the scion in order to avoid injury from excess flow of sap. Reed (17), Stoke (27), Morris (14), Shessler (21), Sitton (23), and others have described methods of preparing and setting scions in the stock. All writers agree that greater success is secured when dormant scions are set relatively late in the season. Becker (2) stated that greater success was secured when scions were set from time leaves were full-grown until catkins fell. Protection of the scion by waxes, paper bags, and shading has been advocated by Morris (14), MacDaniels (11), Shelton (20), Shessler (21), and others.

Propagation by Budding

The shield or T bud has not been considered suitable for thick-barked trees such as hickory and walnut due to the difficulty of preventing "air-pockets" beneath the bark. Shaving the edges of the bark at the side of the shield may eliminate this difficulty. Joley (9), reported variable success in shield budding of walnut in California. Patch budding, either by the annular method or with the Jones patch-budding tool was described by Reed (17), and is reported by Chase (6), Zarger (30), and others to be the most practical method of propagation with walnuts. Pecans and hickories are commonly patch-budded in summer in commercial nurseries. The thin-barked Chinese chestnut is usually budded by the shield-or T-bud method as reported by Hardy (8) and McKay (12).

Scion and Budstick Handling

Sitton (22) reported that two-year wood of black walnut was superior to either older or younger wood. MacDaniels (11) advocated the base of the scion to be in the two-year wood and the tip in the one-year wood.

Shelton (19) reported that scions could be kept moist until used by storing in a closed container with a small amount of sodium sulphate, commonly known as "Glauber's salt". The usual method of scion storage is to pack in moist but not wet peat or sphagnum moss and place in a refrigerator at about 35° F. Waxes and resins have been used successfully to prevent undue loss from the plant tissues while in storage.

Waxes and Dressings

Propagators seldom agree in their choice of a wax and wound dressing. In a series of carefully controlled tests, Sitton (23), found that a rosin and beeswax mixture with a filler gave results with pecans superior to the so-called "cold waxes" or asphalt emulsions. Paraffin and polyvinyl resin are often used for scion covering and to protect newly set buds. Shelton (20) has indicated certain qualities of a satisfactory wax.

The Rootstock Problem

In the Pacific Northwest Painter (16) stated that some Persian walnut varieties on _Juglans hindsi_ (the northern California black walnut) develop a fatal graft blight due to delayed incompatibility at about 20 years of age. This is the so-called black-line disease. McKay (12) found great differences in survival of buds of Chinese chestnut placed on five seedling strains and Hardy (8) suggested that more attention should be paid to the parental relationship of stock and scion in the chestnut. Weschcke (28) reported that black walnuts grafted on butternuts yielded poor crops and that bitternut was a satisfactory stock for shagbark varieties and shagbark hybrids. Smith (25) advocated shagbark stocks for shagbark varieties but found bitternut to be practically as good. Stoke (26), and Smith (25) found eastern black walnut to be the best stock for all walnut species, including heartnuts and butternuts.

Nursery Practices

Commercial nurseries have adopted various methods to discourage the normal tap-rooting habit of nut trees and stimulate lateral and fibrous root production. Planting seed over screen wire, undercutting the seedling each year in the nursery row, frequent transplanting, and root pruning are methods commonly used. Attention must be given to the production of an adequate root system to help the grafted tree withstand the shock of transplanting to its permanent location.

Summary

The chief obstacle to the large scale growing of selected nut varieties is the difficulty in propagation. Careful workers with a background of knowledge and experience and skilled in craftmanship are successful in a limited way. Quantity production is apparently dependent upon specialized facilities and efficient labor programs. The need for extensive rootstock research is keenly felt by growers of walnut, hickory and chestnut.

Literature Cited

1. Barton, Lela V.--Seedling Production in _Carya ovata_, _Juglans cinerea_, and _Juglans nigra_. Cont. Boyce Thompson Inst. _8_:1-5. 1936

2. Becker, Gilbert--Notes from Southwestern Michigan. Rept. North. Nut Grow. Assoc. _28_:135. 1937

3. Bernath, Stephen--Propagating Nut Trees under Glass. Rept. North. Nut Grow. Assoc. _37_:90. 1946

4. Chase, Spencer B.--Black Walnut Nursery Studies. Rept. North. Nut Grow. Assoc. _37_:40-41. 1946

5. Chase, Spencer B.--Eastern Black Walnut Germination and Seedbed Studies. Jour. For. =45=:661-668. 1947

6. Chase, Spencer B.--Budding and Grafting Eastern Black Walnut. Proc. Amer. Soc. Hort. Sci. _38_:175-180. 1947

7. Gellatly, J. U.--Notes on Nuts and New Combinations of Old Principles. Rept. North. Nut Grow. Assoc. _29_:115-120. 1938

8. Hardy, Max B.--The Propagation of Chinese Chestnuts. Rept. North. Nut Grow. Assoc. _40_:121-126. 1949

9. Joley, Lloyd E.--Personal Correspondence. July, 1951

10. Lounsberry, C. C.--Bench Grafting of Black Walnuts. Rept. North. Nut Grow. Assoc. _28_:60. 1937

11 MacDaniels, L. H.--Some Experiences in Nut Tree Grafting at Ithaca, New York. Rept. North. Nut Grow. Assoc. _28_:52. 1937

12. McKay, J. W.--Results of a Chinese Chestnut Rootstock Experiment. Rept. North. Nut Grow. Assoc. _38_:83-84. 1947

13. Morris, R. T.--Top Working Hickories--Rept. North. Nut Grow. Assoc. _11_:105. 1920

14. Morris, R. T.--Nut Growing. 1931. Macmillan, New York

15. O'Rourke, F. L.--Unpublished data. 1940-1945

16. Painter, John H.--Personal Correspondence. July-August, 1951

17. Reed, C. A.--Nut-Tree Propagation. U.S. Dept. of Agr. Farmers' Bul. 1501. 1926

18. Reed, C. A.--Seedling Chestnut Trees versus Grafted Varieties. Rept. North. Nut Grow. Assoc. _32_:79. 1941

19. Shelton, E. M.--Glauber's Salt for Humidity Control in Scion Storage. Rept. North. Nut Grow. Assoc. _28_:70-71 1937

20. Shelton, E. J.--A Laboratory Experience in Testing Wax Mixtures for Use in Plant Propagation. Rept. North. Nut Grow. Assoc. _28_:72-75. 1937

21. Shessler, Sylvester--Grafting Walnuts in Ohio. Rept. North. Nut Grow. Assoc. _39_:145. 1948

22. Sitton, B. G.--Vegetative Propagation of the Black Walnut. Mich. Agr. Expt. Sta. Tech. Bul. 119. 1931

23. Sitton, B. G.--Pecan Grafting Methods and Waxes. U. S. Dept. Agr. Circ. 545. 1940

24. Slate, George L.--Grafting Walnuts in the Greenhouse. Rept. North Nut Grow. Assoc. _39_:146-147. 1948

25. Smith, Gilbert L.--Our Experience with Rootstocks. Rept. North Nut Grow. Assoc. _40_:62-64. 1949

26. Stoke, H. F.--Nut Nursery Notes--Rept. North. Nut Grow. Assoc. _34_:96. 1943

27. Stoke, H. G.--Grafting Methods Adapted to Nut Trees. Rept. North. Nut Grow. Assoc. _37_:99-102. 1946

28. Weschcke, Carl--The Importance of Stock and Scion Relationship in Hickory and Walnut. Rept. North. Nut Grow. Assoc. _39_:190-195. 1948

29. Wilkinson, J. F--Preparation of Stocks for Propagation. Rept. North. Nut Grow. Assoc. _28_:65-66. 1937

30. Zarger, Thomas G.--Nut-testing, Propagation, and Planting Experience of 90 Black Walnut Selections. Rept. Nut Grow. Assoc. _36_:23-30. 1945

Nut Rootstock Material in Western Michigan

Harry P. Burgart, _Union City, Michigan_

It is only natural that those who propagate by budding and grafting are always hoping to find a rootstock that will accept their scions with the highest percentage of takes and impart vigorous growth to the scion variety. Sometimes in our eagerness to adopt a new rootstock we are likely to neglect a vital point, namely--Future Performance of the root-top combination we are about to use.

It would take years of observation in a test planting to prove whether or not a new rootstock material is safe to use. A rootstock can affect the tree it supports in various ways. Sometimes the rootstock will force to the top too much growth, which is likely to bring about unfruitfulness. In other cases, the rootstock may cause a dwarfing habit in the future tree, with the resulting top being a scant producer of nuts. Then there is the combination where rootstock and top vary too much in their growth rate, thus making an unsightly tree. The ideal rootstock is one that attains a diameter nearly equal to the diameter of its partner, and is capable of producing a moderate amount of top growth, together with the production of heavy crops of nuts. Such a rootstock should also accept buds or grafts readily, and be compatible with the scion throughout the life of the tree.

My first experience with rootstocks for grafting came about in 1926 when I was working at the J. F. Jones Nursery then at Lancaster, Pennsylvania. Mr. Jones used both bitternut and pecan seedling stocks for grafting shagbark hickories. Pecans and hicans were also grafted on hardy northern pecan seedlings, and Japanese walnut stocks were used for butternuts and heartnuts. Black and Persian walnut scions were set on eastern black walnut seedlings.

When I returned to Michigan I brought back enough of Mr. Jones' trees for a small test planting here at Union City. These trees were planted in a heavy quack grass sod and some were lost, but those surviving show good compatibility between the top and root.

In the intervening years I have made but slight changes in the rootstock material used in my own nursery. I do not approve of the performance of our butternut varieties on the Japanese walnut _root_, as it results in a weak and dwarfed tree. The use of butternut rootstocks is also unsatisfactory, for they tend to produce trees of low vitality that in a few years fall victim to blight and then perish. I tried our Michigan black walnut seedlings as a rootstock and found that they are very much better rootstock material. The growth at the union is about equal. Top growth is good, and the butternut tops bear early and heavily, with no signs of blight during the ten years I have had them under test.

After years of test I have decided to use the northern pecan seedlings as rootstocks for my shagbarks, pecans, and hicans because they are a fast growing stock tree. They accept the grafts readily, and make good unions more quickly than the bitternut stocks I have tried. Mr. Wilkinson, from whom I obtain my seed, has never failed to send me seed with good viability, just about every seed germinating. The northern pecan seedlings have shown no winter injury here in Southern Michigan during the 20 years I have watched them growing.

An example of the superiority of the black walnut over the Persian walnut as a rootstock is a seedling of the variety Wiltz Mayette growing near a Broadview grafted on black walnut. Both trees are the same age, but the Broadview on black walnut is just about twice the size of its own-rooted neighbor.

Hudson Valley Experience with Nut Tree Understocks

Gilbert L. Smith, _Millerton, N. Y._

This report is not based on any planned or well conducted experiments, but is based simply on our observations of results of our grafting work over the years since 1934.

Our first work was with hickories, so I will start with them.

Our first year's grafting was done in a plot of practically pure pignut stocks. This was the seven leaflet pignut, which I believe to be _Carya glabra_. I have never been sure of the identification of the two species of pignuts. We secured a fairly good percentage of living grafts, which grew well the first summer. The next spring all of the grafts failed to leaf out and later were found to be dead. A few grafts which were put on bitternut stocks (_Carya cordiformis_) grew well, and are still growing well after more than fifteen years. Several different varieties of shagbark hickory scions were used in this grafting.

The second year, we again grafted as many or more stocks in this same area. The results were exactly the same, except that we used some scions of Davis and Fox. (These varieties were brought to light through the contests of the previous winter). The grafts of Davis grew on pignut stocks, are still alive and doing fairly well. They have been bearing for several years, although the squirrels have stolen all of the nuts. Grafts of all other varieties which were on the pignut stocks died the next spring. One graft of Fox on mockernut lived and has continued to grow fairly well. That same year we started our test orchard of shagbark stocks (_Carya ovata_) in a different area. Grafts on these stocks have grown very well.

I believe that for some reason grafts of shagbark on pignut stocks cannot stand cold weather. Certainly, incompatibility is very marked.

Our experience with hickory stocks to date is as follows:

PIGNUT (_Carya glabra_ or possibly _Carya ovalis_). This species is worthless as a stock for shagbark, shellbark, and hybrids of these species. If nut growers have some pignut stocks growing where they especially wish to have some good hickory trees, they can graft them to Davis. We have also heard that Brooks will grow on pignut stocks.

MOCKERNUT (_Carya alba_). This species is also nearly worthless as a stock for shagbark, shell bark, and hybrids, although many more varieties will live on it than will on pignut stocks.

SHAGBARK (_Carya ovata_). This species makes the most dependable stock of any we have tried so far, for shagbark, shell bark, and the hybrids. Its greatest drawback is the long time it takes to grow seedlings to a size large enough to graft.

SHELLBARK (_Carya laciniosa_). We have never had an opportunity to use this species as a stock. I think that it would make a good one and possibly be faster growing than shagbark.

BITTERNUT (_Carya cordiformis_). We have found that this species makes a very satisfactory stock for shagbark and hybrid grafts. We have not tried shellbark on it, except Berger which grows well on it. Seedlings of this species are much faster growing than are shagbark seedlings, and thus are large enough to graft sooner. We have grafts growing on bitternut stocks since 1935, they are growing and producing well. We consider this species as good or nearly as good as shagbark as a stock.

We have received contrary reports from farther south. These may be due to stock being blamed for something they did not cause or it may be that bitternut stocks grown from seed of more southern origin may not be as good as our northern stock.[18]

PECAN (_Carya pecan_). Our experience with this species as a stock is very limited and has been confined to grafts of only one variety of shagbark (Wilcox). Results were very disappointing, but we have been told by others that it makes a good stock. It is much faster growing than is shagbark.

Walnut

In walnut grafting, we have found that the eastern black walnut stocks are so much superior to any others we have been able to find, that we have discarded all others.

BUTTERNUT (_Juglans cinerea_). We have found that it is much harder to secure living grafts on this stock than on black walnut. It also attracts butternut curculio to the nursery.

JAPANESE WALNUT (_Juglans sieboldiana_ and variety _cordiformis_). We have found that seedlings grown from either of these species are a great attraction to the butternut curculio. They are more difficult to secure living grafts on, and grafts on these stocks are very definitely less hardy than similar grafts on black walnut growing side by side. We have proved this repeatedly.

PERSIAN WALNUT (_Juglans regia_). We have never used this species as a stock, and in view of the fact that grafts of it grow so well on black walnut stocks, I can see no use in even trying it.

EASTERN BLACK WALNUT (_Juglans nigra_). As stated above, we have found this to be the ideal stock for all walnut grafting. It is more free from insects than any of the other walnuts. Grafts grow well on it and are more hardy than grafts on some of the others.

We have not had enough experience in grafting chestnuts and filberts even to offer any comment as to stocks for them.

FOOTNOTES:

[Footnote 18: The planting location perhaps has more influence than the seed source. At any rate, the poorest growing pecan in the University of Illinois orchard is on a Wisconsin bitternut understock.--J. C. McD.]

The 1950 Persian Walnut Contest

Spencer B. Chase, _Contest Chairman, Tennessee Valley Authority, Norris, Tennessee_

The nationwide Persian Walnut Contest conducted by NNGA in 1950 attracted 33 entries from 11 states. The contest was judged by H. L. Crane, L. H. MacDaniels, and H. F. Stoke, assisted by S. B. Chase.

The entries were first evaluated independently by the judges. Then each judge made a second evaluation with the knowledge of the findings of the other two judges. The Chairman then arbitrated the differences of opinion among the three judges. This action amounted only to the placing of four entries after the first prize had been unanimously agreed upon.

The following table shows the results of the contest: