Chapter C: C. LOUNSBERRY, Iowa State College (1)

This subject, the structure of the walnut, is discussed in its relation to propagation. Catkin bearing nut trees, such as the walnut, have a refined structure that makes grafting difficult. Structure, rather than form of walnuts, suggests treatment under the headings, bark, cambium, wood, roots, pith and buds, as well as the sap that permeates them.

=Bark:= When the bark of the walnut is cut, as in budding, it is difficult to tie down so it will not curl and yet not strangle the bud. The wax-like covering of the bark is thin. However, the bark itself will stay green two months or more if weather is cool.

=Cambium:= The cambium dries quickly when exposed to air, and must be kept covered. Grafted walnuts show callus growth from the cambium, and also from the pith of stems and the endodermis of the root.

=Wood:= The wood of the walnut is diffuse porous, brittle, straight grained, and easily split. The wood must be cut diagonally to get sufficient tension to hold the scion in grafting. The branch grows rapidly in a short season, May 15th to July 1st in central Iowa. The upper two-thirds of the one year growth is usually light weight with pith of large diameter. The base of the one-year growth is the best for scions. Some varieties of walnut as for example the Thomas, have relatively large one-year growth and more scions can be cut from its branches than from the wood of Ohio which is small and willow-like.

Measurements taken in 1940 on 118 common black walnut seedlings planted in 1939 showed 9/16" average diameter of seedling at crown, 5/16" average diameter of pith at crown; 3/8" average diameter of seedling at top; and 1/4" average diameter of pith at top; 3.26 inches average length of solid pith above crown; 2.91 inches average length of solid pith in root below crown.

=Pith:= Pith in the black walnut is chambered (lamellate) in the older wood, but solid in the younger, growing wood. The plates are a light brown color, getting larger in diameter toward the top of the year's growth. The leaf traces from the leaf rachis to the pith show heavier from the bottom buds of the branch than at the tip, and the pith is usually solid at the bottom of the branch.

=Roots:= When the nut of the black walnut germinates in the soil the lobes or cotyledons do not rise above the ground like the cotyledons of the bean but remain in the nut shell under ground, and are broken off in the growth of the seedling, the root going down and the stem rising above the ground. Where the cotyledons are broken off, the so-called crown of the walnut, two rough places appear, nearly opposite on the stem. In these rough places, two groups of buds are formed, rarely three groups.

Cytological studies at Iowa State College have not shown why there are not stem initials in the tap roots of the walnut. When the root is cut off a foot underground, root initials develop but no stem initials. The sensitivity of walnut leaf buds to water may have something to do with it.

=Buds:= Buds of the walnut are in vertical groups of two or three in the axils of the leaves. They have few scales. They appear on seedlings and current year branches. Some have short stalks. If broken off they do not usually grow back again. The second year, these buds usually drop off in mid-season. In cutting off buds, unless the group of buds is taken out as a chip, some may grow out again.

=Leaf arrangement:= There is a three rank arrangement of leaves in the walnut, the ninth leaf coming in the same position as the first. According to the work of Caesalpino, the buds should then rise in three places at the crown. Only in rare cases does this occur in the black walnut, although it is usual with the Persian walnut. If the nut is planted deep this causes much suckering and a tendency to etiolate the buds so they will stand water.

=Buds are sensitive:= Buds are sensitive to water, and storage material must be fairly dry and cool. In two large boxes of scions received last year from Germany, some 20 varieties of Persian walnut, all had dead buds when received. They were packed in German peat. When buds are covered with wax the wax must not be too hot or it will kill the buds. In placing grafted walnuts in sphagnum or sand they should not stay wet or the buds will die. Either unions must be above damp sand or sphagnum, or the buds be protected by wax or adhesive.

=Sap:= In spring grafting there is an enormous flow of sap which will sometimes tear the plates out of the pith. Grafts may be protected by girdling the stock a few inches below the place where the graft is set, or both above and below it. In 1937 259 walnuts three years old were cut off six inches above the ground and girdled two inches above the ground. 171 crown buds came up, 88 started above the girdling. 207 trees were cut off three feet above the ground, and the trunk girdled six inches above the ground. 153 started above the crown, and 90 started above the girdle. The same year (1937) 195 trees three years old were cut off four feet above the ground, and all buds above ground were cut flush with the surface of the bark. This was repeated twice, finally taking buds out as a chip, except the top bud; 126 died; 69 grew from the top but. 203 trees three years old were cut off five feet above ground and all buds cut off except upper one; 64 died; 139 grew from top bud. 200 trees three years old were cut off six feet above ground, and all buds kept rubbed off except top one; 33 died, and 167 grew from top bud.

=Vitality and sap:= Black walnut sap changes color from oxidation almost instantly. Bench grafts must be made quickly and put in place at once or the unions will dry out. If the root does not stain hands in grafting the graft usually fails. In outdoor grafting if the sap stands in pockets the sugar will ferment, killing the graft. There is a new Jersey (3) bulletin which shows black walnut sap as unstable, quickly forming sugar when exposed to warm weather.

=Vegetative propagation of greenwood cuttings:= Witt and Spence (4) in England working with greenwood cuttings attained 75 per cent success with Persian walnut and Royal walnut in July and August. They had no success with black walnut at that time (1926). The Germans in 1936 (1) working on greenwood cuttings had most success with the Persian walnut, but used greenwood taken in September.

=Vegetative propagation or hardwood cuttings:= In 1938 the author (2) using growth substance on saddle grafts of various walnuts found Asiatic and western walnuts went on their own roots. At this time the Tasterite black walnut went on its own root. In 1946 and 1947 using about 25 varieties of black walnut, Persian, western and Asiatic walnuts, eight inch hardwood cuttings were used beginning in December and repeated in the spring of 1947. Nearly all the cuttings of the larger size (about 1/2") started in about a month and grew about two months. Then all died. There were balls of callus on many of them. One on Thomas was an inch in diameter. The bottom heat was held at 70 degrees F. This may have been too high, as on raising the cuttings it was found the callus had rotted. This procedure has possibilities.

Literature Cited

1. Institut fur Obstbau, Berlin. Die Walnusz veredlung. (Vegetative propagation of walnuts). Merkbl. Inst. Obstb. Berlin 5, pp. 15, 1936.

2. Lounsberry, C. C. Use of Growth Substance in Bench Grafting Walnuts and Hickories. Northern Nut Growers Association 1938 Report, p. 63.

3. Nelson, Julius. Fermentation and Germ Life. N. J. Ag. Exp. Sta. Bul. 134, 1899.

4. Witt, A. W. and Howard Spence. Vegetative Propagation of Walnuts. Ann. Rep. East Malling Res. Station 1926-27.

A Method of Budding Walnuts

H. LYNN TUTTLE, Clarkston, Wash.

It took man some thirty thousand years to learn to build a fire--conveniently. I thought it was going to take me that long to learn how to bud walnuts, but fortunately the period has been somewhat shortened.

When I first began to propagate, or try to propagate, walnuts, I naturally looked to the approved and accepted methods. For me, they did not work. Before I was through I think I tried them all. I patch-budded with variations and improvisations. I shield-budded and bark-grafted. I coated the wounds with grafting-wax, latex, cellophane, asphalt and paraffine. I trimmed off the bud shoulders to make a smoother tie and trimmed around the edges to make more contact. I wrapped with raffia, strings, rags and rubber strips and tacked with small nails. Whatever I did or however I did it results were all about the same--the sap soured. In fact over a period of years I tried every way I could think up or read about to bring the bud and the cambium layer together and make them stick. Results were surprisingly uniform--the sap soured.

But we must not dwell too long on the shots that missed. As with a refractory engine that will suddenly sputter, there came some elements of success. The point to learn was, why? Concentrating on the shield bud entirely we determined to find these whys. So we tried taking big slabs of bark along with the bud, peeling out the wood, breaking off the leaf stem entirely and waxing the scar and making an unnecessarily long cut for the bud. The bark stuck fairly well but the buds died. This was some encouragement and I knew that with enough time, reason and a little luck we would eventually hit the mark.

Now Dame Fortune had decreed that I be raised on a grain and stock ranch where the only trees we could see were in the distant mountains, or, if we rode in the canyons, cottonwoods and choke-cherries. My experience and training was with animals, and animals, especially horses, seem quite susceptible to accident. The first principle of treating almost any wound is to give it drainage, otherwise, both literally and figuratively, the "sap" soured. Thus it dawned on me that a tree-wound, even if only skin deep should have the same treatment as a flesh wound. And drainage, being desirable, should be ample.

It was quite late in the season but I went out and set a dozen Schafer walnut buds on eastern black stocks. These buds HAD DRAINAGE. The vertical cut of the T extended at least two inches below the bud. Success ensued, they grew. The following spring we budded as soon as the bark would slip and continued at intervals all summer. Results were good. Some of the steps we now use are probably not essential and perhaps not even the best, but there are two points that cannot be over-emphasized, namely, drainage and contact. The complete method is as follows: 1. Trim bud sticks to leave an inch of petiole on the bud. 2. Make the T cut with a long vertical slash that will extend at least an inch below the bottom of the bud. 3. Cut the bud long and deep and peel it from the wood by pinching the sides. Be carefull not to injure the bark just below the bud. 4. Insert the bud either flush with or below the cross-cut. 5. Wrap with large sized rubber budding strips just firmly enough to make good contact. Too tight wrappings curtail circulation. Do not cover the cut below the bud. The wound must have =drainage=. 6. Be sure that the center of the bud-cut is firm against the cambium layer. If it humps of bows and won't stay down insert a tooth-pick or bit of leaf stem or something along the center line to hold it down. We usually do this during the wrapping process.

We use no wax. We throw a wrap over the bud, shoulders even though it may press the petiole forward against the bud. If the center of the bud pulls out it will not grow although an adventitious bud may eventually start. Budding seems about equally successful any time that the bark slips freely. On walnuts this is all summer if not too dry.

Early-placed buds may make several feet growth before fall if sufficient moisture is available. On walnuts there are always dormant buds. We have used storage wood but now just cut it fresh. We have not tried draining patch-bud or grafts. Although we have not tried it we think cherries and other trees inclined to drown the buds might be better handled in this manner. Climate is a factor in the type of propagation advisable. One very fine grower using buds in California could propagate only by grafts when he moved to Western Oregon.

The kernel of my walnut budding experience may well be summarized in one word--drainage.

* * * * *

Questions asked Mr. Stoke after his demonstration of grafting and budding. [See his paper in 1946 Report, pp. 99-103.--Ed.]

Member: "How do you keep your scions?"

Stoke: "I prefer 'orange' cold storage for scionwood. This is just above freezing. Walnuts should be in full leaf before spring budding."

McDaniel: "What percentage of chestnuts did well with the 'plate' method of budding?"

Stoke: "I don't use it with chestnuts for spring budding, but sometimes for summer budding. It will work well on any variety of Persian walnut, heartnut and black walnut. Place buds on the north and northeast side of tree to prevent sun injury."

Question: "Do you find any difference in using buds from an eight or ten year old tree as against a younger tree?"

Stoke: "No, not so long as it is healthy. For spring budding I don't care to have any trees too vigorous. Cut tops off young trees three to five days after budding, and force the buds into growth. If you delay too long the bud will die. I wouldn't try to bud trees unless bark is slipping."

Member: "I have used parapin wax and covered it with old bread paper."

Stoke: "That may work because the wax was shaded. Southern sun may melt parapin and paraffin waxes."

Mr. Corsan: "Dentists, surgeons and wood carvers make the best grafters."

Question: "Can the scions be cut with a small plane?"

Stoke: "Anything you have to cut with a plane is too big. I never use a plane."

Question: "What do you use a splice graft for?"

Stoke: "Anything except walnut. In walnut I use a modified cleft graft, and I take care of the sap flow by placing the graft down about 1" or 1-1/4" below the cut (where the tree is cut off). Wax the scion but do not wax the cut. Let it bleed."

Question: "What is the value of cut leaf black walnut?"

Stoke: "Purely ornamental. Weschcke reports that it is very hardy with him."

Rick: "What about the Lamb walnut?"

Stoke: "We don't know whether the wood of grafted trees is curly or not. I sent Mr. Reed a limb from Lamb and he gave it to the forest laboratory and they found no evidence of curly grain."

Rick: "Shouldn't it be propagated until we are sure?"

Stoke: "We had Mr. Lamb himself talk before us at Roanoke and he told us about the parent tree. He doesn't know what makes one tree curly and another not."

Korn: "Is that uncommon?"

Stoke: "Not so very. Trees are most curly at the base and in the outer wood."

Question: "Do you always leave that stub on black walnut?"

Stoke: "Yes, but it should be removed later in the first summer."

Question: "Where do you use your splice graft."

Stoke: "On anything other than walnut, if scion and stock are the same size. Where stock is larger than scion I use the modified cleft graft up to sizes approaching one inch in the stock. For topworking larger stocks I use one of the forms of bark graft. For the large hickory stock Dr. Morris' bark slot graft is preferred. For large, thin-barked stocks the simple bark graft may be used. My original grafts of the Carr and Hobson Chinese chestnuts, made with scions received from Messrs. Carr and Hobson in the winter of 1932, are still perfect unions.

"I believe that grafted chestnuts growing in frost pockets are most likely to develop faulty unions; possibly frost injury to immature cells at the junction point may occur. Dr. Crane mentions a similar failure of unions between Persian and black walnuts on the Pacific Coast."

Dr. Crane: "What cut did you use in grafting those chestnuts?"

Stoke: "Modified cleft. In using Dr. Morris' bark slot graft I find it best to leave just a little of the cut face of the scion wedge above the top of the stock. This, with top of the stock cut sloping away from the scion, as illustrated, promotes quick healing with no 'die-back.'"

Dr. Smith: "Is that top slanting?"

Stoke: "Yes, I cut it slanting."

Dr. MacDaniels: "That is a good graft for walnuts, too."

Note: Mr. Stoke showed the group a picture of a mockernut tree in one of his fields which he had girdled to kill it. The tree lived four years and during those years the moisture had to go up through the inner wood.

The substance of Mr. Stoke's talk, together with illustrations, may be found on page 99 of the 1946 report.

Importance of Bud Selection in the Grafting of Nut Trees

G. J. KORN, Kalamazoo, Michigan

For many years the fruit growers have been improving the qualities of their fruits in several ways. The early pioneers of our country selected the best fruits from seedling trees. Chance seedlings that were found in pastures, by roadsides, or possibly in some out-of-the-way place, selected because of some special quality or group of qualities, still dominate our commercial plantings of fruits and nuts. Several of the apple varieties to be found in the market today are from these chance seedlings.

In more recent years some of our agricultural colleges have been breeding fruits. Such breeding has given us several of our more promising named varieties. In this way a great improvement has been brought about in our fruits.

Environment too appears to have played an important part in making changes in fruits and nuts. Nuts that are extremely hardy in the more northern latitudes, appear to have developed this hardiness gradually throughout many generations. Because of this quality we are now able to select varieties that are most likely to succeed in any particular locality.

More rapid and satisfactory methods of improving our fruits and nuts have been brought about through breeding. This development of the science of plant breeding has made it possible to blend the good qualities of two seedlings into a new variety. Man does not have to follow nature's slow hit-and-miss method of developing more desirable qualities in her products. Controlled breeding, as brought about by man, produces faster and more satisfactory results. Man's improvement over nature has come about through his choice of the qualities to be blended, and his ability to bring together two parents from widely separated parts of the earth, if necessary.

Besides breeding, we are able also to use some of the mutations or bud sports to improve our nuts as well as fruits. Although our progress in improving nuts may not yet be as spectacular as cross-breeding with apples, bud selection has already modified the list of our commercial varieties.

One of the first requisites in bud selection is so thorough a knowledge of the variety that any departure from the type will be detected. Then it will be necessary to start propagation to determine whether the variation was caused by some environmental factor, or is really a sport which can be perpetuated by vegetative propagation. You may wonder if many of our nut growers know nut varieties well enough to detect any but the most obvious sports. Nut improvement through bud selection within the variety lies ahead of us.

Among fruit growers the search seems to have been for fruits of different or more pleasing color. As nut growers we are more likely to be interested in nut sports having better size, kernel, cracking qualities, etc. Trees that are able to ripen their nuts in short or cool seasons are especially desirable in some of our more northern states.

My attention was especially called to the importance of bud selection several years ago while buying my winter's supply of apples. I was examining the splendid crop of Jonathan apples in a neighbor's large commercial orchard. On most of the Jonathan trees the apples were large and well colored and the crop was heavy. However, a few trees bore apples of inferior size and color. Upon questioning the fruit grower as to the difference in the performance of the two types of Jonathan apple trees, he explained that the better apples came from trees supplied by a nurseryman who was very particular in selecting a good bud strain. The other trees were just the ordinary strain of Jonathan.

It was while working in a commercial orchard of the grafted varieties of black walnuts that I noticed one especially promising Thomas tree. During the few years that I have observed this tree, its nuts have been of splendid size and very uniform. The kernels from the nuts from this tree were somewhat better than those from most of the other trees. I now have some grafts growing from this promising tree.

There appears to be much promise for nut improvement by cross-breeding to regroup desired qualities. Although many of us enjoy the nut contests that are conducted from time to time, it appears that our nut improvement program might move along faster if more attention were given to nut breeding and searching out desirable bud sports.

Discussion after G. J. Korn's paper.

Corsan: "Farmers should be encouraged to plant nut trees along boundary lines. Enormous amounts of fertilizer there."

J. R. Smith: "One tree in ten thousand seedlings is worth while."

Dr. Lounsberry: "We have two trees planted close together--one bears small nuts and the other large nuts. They are from the same grafting. It would seem that the trouble is in the stock. The stock makes a vast difference."

The Hemming Chinese Chestnuts

E. SAM HEMMING, Easton, Maryland

The bearing record of our row of 18 Chinese chestnuts has attracted so much attention that I thought the Association would be interested in seeing some slides of these trees, also of our experimental orchard, as well as the large quantity of small trees we grow in our nursery and the manner in which we raise them.

You will see a number of slides of chestnut trees and hear a lot about the bearing qualities, but you won't see a single nut, for unfortunately all these slides were taken between December 1946 and July 1947. You will just have to let the numerous little trees attest to the fact that these trees bear. We have 50,000 trees in our nursery.

These trees are now nineteen years old and have borne rather remarkably since 1937. They are spaced too close--an accident--but I believe that helps thorough pollination. They are now 12 and more inches in diameter, some are 30' high and the spread is at least 35' where they have the room. All but No. 14 are spreading in character; spreading character and good bearing seemed to be connected.

The bearing record of these trees has been given before but I will summarize them by years again: 1937--118 pounds; 1938 (no records); 1939-463 pounds; 1940--250 pounds; 1941--564 pounds; 1942--658 pounds; 1943--749 pounds; 1944--678 pounds; 1945--250 pounds; 1946--1,100 pounds; this year's crop will probably run 700 to 800 pounds.

The trees seem to bear much the same, with No. 14 the poorest and No. 19 the best and, like many other tree crops, they tend to alternate good and poor crops on each tree. The nuts are of good size, averaging 40 to 50 per pound (green) with No. 6 and No. 19 bearing the smallest nuts. They ripen in September with the exception of No. 19 which is a month later. Mr. Reed likes No. 16 which has a wrinkled shell. All the nuts are medium sweet to sweet and all of them fall free of the bur. I think the most significant thing is that at least 12 of the trees have nut characteristics so near alike that they are about indistinguishable, which certainly makes them a good source of seed.

The similarity of the nuts brings up the controversial subject of the seedling raised tree, and I will make some remarks in defense of this method.

1. All our parent trees are good bearers.

2. There is no extraneous pollen in the vicinity.

3. I will present as a question: Has the Chinese chestnut, like the rose and the apple been hybridized out of all semblance of the wild form?

4. The seedling tree should bring chestnuts to the average householder's table 30 years sooner than grafting will.

5. We now produce a 3'-4' tree for a very reasonable figure.

6. All varietal forms at present are as yet unstabilized (most varieties of 10 years ago have been discarded). There will probably be some duds in seedling trees, but we've had no local complaints and I wonder if they will exceed the "troubles" found in the grafted tree. We have had customers brag about what their 2 or 3 or 6 trees bore.

To prove our faith in this method we planted a test orchard. When the trees were 3 years old from 2 year transplants they bore 25 pounds. Next year, 1944, they bore 800 pounds or an average of 1 pound per tree. Right then and there we thought that we would have a real story to tell, but we had misfortune in another direction. Three years in a row we have had frosts when 6 inches of new growth were on these trees (the orchard is not as well situated as the parent trees in this respect). So we had no crops worth mentioning but neither did we have strawberries or similar fruits. This year the orchard was frosted 2/3 the way to the top so we will get quite a few nuts, maybe 500 pounds. Incidentally, we have been here 25 years and we've not had frosts like these before.

We use all of our good nuts for seed purposes, grading out all small or damaged nuts. In raising these trees, even from seed, we've had our troubles. We let them cure several weeks then plant them in well fed soil in a narrow trench about 2 inches deep. We place the nuts 5 or 6 inches apart; we fill the trench with sawdust level with the surface. We mound the soil over this about 4 inches until spring. Then it is removed. This method lets the shoots through, otherwise they tend to send 3 or 4 stems. The nut sends down the root very early in the spring. We have some trouble with the mole-mice combination; for this reason heavy soil and sawdust is better than sandy soil. As you know neither the nut nor the tree likes wet soil.

In raising the young tree the principal difficulty is in getting a trunked upright tree. A seedling, especially when transplanted the first year, flops all over like a flowering shrub. To get them up we plant them fairly close, prune them, and feed them. Our 1 year trees are usually two feet high and 2 year trees are 4 to 5 feet high. We wholesale our trees mostly to mail order nurseries and the largest had a 5% request for replacements.

There are troubles in growing Chinese chestnuts just as there are in most fruits and nut crops and, in a way, I am glad there are because I am of the opinion there is no such thing as harvesting without cultivation. For instance, if you plant them and let nature take its course--it will. It will on an apple, too.

We have found a few small lesions of chestnut blight which were removed by pruning and then painted with pine tar. They usually occurred at a previous point of pruning. Some of the transplanted seedlings have developed a twig canker at a bud, but I've never seen them kill one and even when we don't prune it out, the tree overcomes it by new growth.

The Japanese beetle attacks the chestnut but, although they were bad this year, one spraying of DDT was effective. The weevil (curculio) was bad enough last year so we are spraying this year. Small growers should put the nuts in metal containers and thus destroy the larvae, if any.

I would like to remark here that we are a nursery growing many ornamentals, and the Chinese chestnut, although low branched, is a very ornamental tree. I know of no tree that has a handsomer dark, shiny green leaf or one whose green color holds so well until frost.

Now I think you will agree I have reported the behavior of our trees fairly, the difficulties of raising the trees, and have emphasized that I doubt if you will get success with the Chinese chestnut without effort; yet in conclusion I would like to step into "fantasy". Our No. 19 tree bore 124 pounds; suppose you had 50 trees per acre bearing that quantity. You would get 6,000 pounds per acre. The European chestnut, which is not as good, brought 30c on the Baltimore market last year. That would mean $1,800.00 per acre. Imagine having 10 acres!

1947 CROP

Pounds of Chestnuts from Original Trees at Eastern Shore Nurseries, Inc.

No. 1, 78; No. 2, 58; No. 3, 51-1/4; No. 4, 7-1/2; No. 5, 49; No. 6, 31; No. 7, 34; No. 8, 31-1/2; No. 9, 63; No. 10, 40-1/2; No. 11, 61-1/2; No. 12, 64-1/2; No. 13, 56; No. 14, 47-1/2; No. 15, 74; No. 16, 60; No. 18, 106; No. 19, 25-1/2--Total, 938-3/4 pounds.

=Young Orchard:= 225-1/2 pounds.

Discussion after E. Sam Hemming's paper

Corsan: "Do you recommend the use of lime?"

Hemming: "We do not use lime. We use Vigoro at the rate of 1 to 1-1/2 lbs. to inch of diameter per tree."

Corsan: "Why do you use Vigoro?"

Hemming: "No particular reason, just that it is available."

Member: "What time of year do you fertilize your trees?"

Hemming: "We fertilize during the winter--usually during December."

Crane: "Last year we used a method of storing Chinese chestnuts which proved very satisfactory. Two thousand pounds of nuts were stored last year. Fall planting is good where one can use it but in a lot of areas it can not be used because of rats robbing the plantings. We have to store the nuts. The procedure we follow is to harvest every other day. Nuts are placed in tin cans with friction top lids. The lids should have one to three holes of 1/16" diameter in them to provide air. Cans are placed in storage at a temperature of 32 to 40 degrees F."

Stoke: "I keep chestnuts in the cellar in a can with an open top in what we call limestone sand. Keep wonderfully well. Chestnuts must have air."

Gravatt: "Down south we have a lot of trouble with decay. We take nuts right from the bur and put them in the soil. They give much better germination."

Crane: "The Chinese harvest their chestnuts just as soon as the bur cracks. They do not wait for the nuts to drop from the trees but harvest the nuts from the trees and store in covered pottery jars. They plant in the fall of the year. They do not hold nuts for any length of time."

Corsan: "How about charcoal?"

G. Smith: "Charcoal is good to store nuts in. They are shipped from China that way."

Smith: "Would chestnuts stand carbon bisulphide for getting the weevil out, or is the hot water treatment better?"

Crane: "Carbon bisulphide treatment is dangerous, it will kill weevils but it will also kill the nuts so they will not germinate. Unless precautions are used it may cause an explosion and fire. Methyl bromide treatment is better."

Stoke: "The hot water treatment is the best. It consists of immersing the nuts in water at 120 degrees F. for forty minutes."

Hemming: "I have raised about 100,000 seedlings and have never seen blight on any of my seedlings."

Dr. Smith: "A tree needs usually to be as big as the small end of a baseball bat before the bark opens enough to let in the blight spores."

Stoke: "Blight begins where there is rough bark which provides lodgment for the spores. Rough bark and moisture result in blight, hence the disease usually starts near the ground."

Crane: "The blight problem in the growing of chestnuts has often been stressed. I think you will have more loss from sunscald and root rot than you will from blight. Blight is a minor trouble with us. The Chinese chestnut naturally grows with a low head. It is a mistake to cut off the low branches on the trees until they attain some size, they can then be cut off."

Stoke: "Regarding the protection of nut trees against winter sun scald, I find that if you take ordinary aluminum paint and paint the south and southwest side of nut trees it will last for two years."

Dr. Smith: "Chestnut trees have blighted for me where the water table was too high and trees of same origin or better drained ground nearby did not blight. Blight is often a sign that the tree wants something it lacks--much like disease in humans."

Results of a Chinese Chestnut Rootstock Experiment

J. W. McKAY[4]

Introduction

The propagation of chestnut species by budding or grafting has been performed by different workers with varying degrees of success. Many have found that grafted trees could be produced and grown successfully but that graft union troubles developed in a certain percentage of the trees either soon after grafting or a few years later. The variety "Carr" is known to graft with difficulty in certain localities and to give a high percentage of poor unions both at the time of grafting and after a few years of growth. The question of relationship of scion and stock has been considered by many workers to have an important bearing on the success of grafting operations but no critical work has been done to determine this point. Some investigators hold that scions of one species may be grafted upon stock of another species without harmful effects. The results of the budding experiment with Chinese chestnut reported in this paper are the first of a series of tests designed to contribute needed information about stock-scion relationship in chestnuts.

[Footnote 4: Associate cytologist, Division of Fruit and Vegetable Crops and Diseases, Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural Research Administration, U. S. Department of Agriculture.]

Description and Results

The five seedling Chinese chestnut trees used in the experiment were selected because of their heavy-bearing tendency and because of the excellent keeping quality of the nuts. Two of the trees bear nuts of large size while the other three bear nuts of medium to small size. Seeds from the five trees were planted before the use of the seedlings as stocks in the budding experiment was planned, and since the seedlings from each tree were planted together replication of the experiment was not possible. However, the stock was grown in thoroughly mixed soil in a coldframe and differences in performance of seedlings could hardly be attributed to soil heterogeneity.

Buds from the five parent trees were placed on the five lots of their own seedlings in all combinations of budwood and stock. The work was done during the first week of September when the bark of both budwood and stock was slipping yet growth had slowed down to some extent. Buds were placed about two inches below soil level on the one-year-old seedlings and the soil pulled back to cover the buds. Budding was done by means of the familiar shield or T-bud method and rubber budding strips were used as a wrap. Budwood was shipped from Albany, Ga., to Beltsville, Md., and was damaged somewhat by high temperature in transit, a factor which may be partially responsible for the overall low percentage of buds that grew.

In referring to the results presented in table I, it will be noted that considerable variation occurred in the performance of the five lots of seedlings as stock, as well as in the take of buds from the five parent trees. The totals in the last column on the right are all equivalent to percentage since 100 buds were placed on each lot of seedlings. In like manner, the totals in the bottom line are all equivalent to percentages since 100 buds of each parent tree were used.

Seedlings of stock D were decidedly inferior to seedlings of stock C in take of buds, and both of these lots of seedlings originated from large nuts. Also, scion e gave a significantly lower take of buds on all lots of seedlings than scions c or d. The scion e tree produces small nuts whereas the scion c and d trees produce large nuts. Scions a and b are intermediate in take of buds, and the source trees both produce small nuts.

Discussion

At least one significant interpretation may be made from the results of this experiment, that may partially explain the difficulties encountered heretofore in propagating chestnuts. Using the take of buds as a criterion it can be stated that in this experiment the five lots of seedlings from known parents differed in their performance as stocks. Moreover, the five parent trees used as a source of budwood differed among themselves in the capacity of their buds to grow when placed on comparable lots of stocks. If these results are correctly interpreted it is clear that both the stock and the scion may influence the success or failure of propagation technique. Doubtless both of these variables have operated together in the propagation of existing varieties and, as would be expected, the results have been unpredictable. It seems likely that the grafting and budding of chestnut varieties should be worked out in the future on the basis of using understocks derived from the seed of special trees or clones found to be suitable sources by tests for grafting performance.

It should be pointed out that the five trees used in this work originated from two lots of seed imported from neighboring localities in China and probably are closely related. The fact that significant differences were obtained in this material furnishes basis for the belief that great variability in the budding performance of the Chinese chestnut is to be encountered in the many introductions that have been made into this country.

Table I. Results of budding each of five Chinese chestnut clones on
its own seedlings and on the seedlings of four other clones. The
figure for each combination represents the number of buds that grew
out of 20 buds placed.

SCION

a b c d e Totals
S A 4 6 4 5 0 19
T B 3 2 8 4 0 17
O C 0 3 8 9 5 25
C D 1 2 3 1 1 8
K E 2 2 7 9 2 22
TOTALS 10 15 30 28 8 91

Discussion After Dr. McKay's Paper

Dr. MacDaniels: "A good scion on chestnut is one problem which we have not solved."

Dr. Smith: "I find both Carr and Hobson difficult to graft and have discontinued them."

Dr. Crane: "In California and Oregon they are having quite a lot of difficulty with graft union failure with Persian walnuts. They have used the Northern California black or Hinds walnut as root stocks. Now they find that in some cases the union fails and results in what is known as the black line disease. At the present time this trouble is the most important cause of the loss of their trees."

Dr. Smith: "Zimmerman is a good bearing variety with a good nut. I find that soil makes some difference with this variety."

Breeding Chestnut Trees: Report for 1946 and 1947

ARTHUR HARMOUNT GRAVES[5]

The chief aim of this breeding work is the development of a chestnut tree of timber type to replace the now practically defunct American species, _Castanea dentata_. For the principal economic value of the chestnut was not in its edible nuts but its valuable timber, the loss of which means at present many millions of dollars subtracted from the assets of the American people; and when we consider the loss for all time in the future the figures become astronomical.

[Footnote 5: Consulting Pathologist, Conn. Agric. Expt. Station; Special Agent, Conn. Geological and Natural History Survey; and Collaborator, Division of Forest Pathology, U. S. Dept. Agriculture.]

_The Chestnut Blight in Italy._ Early in 1946 we received a visit from Captain John B. Woodruff, of Wilton, Connecticut, who told us that while serving as Chairman of the Department of Agriculture and Forestry, and Instructor in Forestry at the Army University Study Center in Florence, Italy, he visited chestnut stands infected with the blight. _Endothia parasitica_ was first discovered by Professor Guido Paoli in 1938 on a private estate in Busalla, about twenty miles north of the seaport city of Genoa. Since then the blight has been detected throughout the province of Genoa in the legion of Liguria; and other widely separated infections have been found. The fungus has been cultured and identified by Professor Biraghi of the Royal Pathological Station in Rome, as _Endothia parasitica_. It is believed to have been present in this region for from five to eight years previous to its discovery. The manner of its introduction into Italy is not known, but since Japan and the U. S. have carried on considerable commerce with Italy, either or both countries are possible sources.

The disease is spreading in Italy at a rapid rate. "By 1942 one half of the 190,000 acres of chestnut in the province of Genoa had been infected and spot infections had been discovered in the adjoining coastal province of La Spezia, also in the region of Liguria."

I am devoting some space to this situation because it means so much to the Italian people. In Italy fifteen percent of the forest is composed of chestnut. Not only does the country use the nuts as a source of food and income, approximately sixty million pounds being exported annually in former years, but the young coppice shoots are used for the weaving of baskets, older ones for poles for vineyards, still older for staves of wine casks, and the oldest for telephone and telegraph poles. "Before the war, chestnut flour was the principal food in many localities, but during the war a serious food shortage forced the people in many other areas to rely solely upon chestnut flour for weeks at a time."

Professor Aldo Pavari, Director of the _Stazione Sperimentale di Selvicoltura_ at Florence, visited this country in the summer and fall of 1946, under the sponsorship of the UNRRA, and spent four days with me at our plantations, learning our methods and getting acquainted with the blight resistant hybrids we have been developing by the breeding together of oriental and native chestnuts. Prof. Pavari visited also the plantation of the Division of Forest Pathology at Beltsville and elsewhere, and other plantations in the west. In December we shipped to Florence, Italy, nuts of our best hybrids, and in March, scions for grafting--also this summer (1947) pollen of some of our best trees. On October 15 of this year (1947) we sent another shipment of nuts. Thus we may be able to give Italy the advantage of the progress we have made to date.

Regarding the susceptibility to the blight of the European or Spanish Chestnut (_C. sativa_) we have had the following experience. Our winter temperatures appear to be too severe for this species. Dying back is sure to occur, at least at our Hamden, Connecticut plantations, marked more or less according to the degree of cold; and on the dead parts _Endothia_ then appears, to later invade the parts still living. In 1932 I received nuts of _C. sativa_ from France from Professor Hochreutiner of the Geneva Botanic Garden, from Professor Uldrich of the Berlin Botanic Garden, and also from France from Dr. Guillaumin of the Jardin de Plantes at Paris. Although I have given the resulting plants much attention they continually die back each year so that we have only two or three individuals that are more than six feet high. But Professor Pavari says in recent correspondence (July 15, 1947) "Referring to Spanish chestnuts, after we have been assured that the fungus we have found and observed on _Castanea crenata_ in Spain is really _Endothia parasitica_, we must admit that our hypothesis may be exact that _Castanea vesca_ [_sativa_] presents in Spain races or types resistant to the disease." He goes on to say that the fact that the chestnut blight is so widespread at Naples and Avellino is at variance with my theory that cold winters are the predisposing cause, for in the regions mentioned the winters are mild and "very warm in comparison with those of Connecticut." The essential fact seems to be that the European or Spanish chestnut is very susceptible to the blight, perhaps as much so as is our native species, but that evidently certain individuals or races exist that are more or less resistant.

During the early part of 1947 we had a visit from Professor Cristos Moulopoulos of the University of Salonika, Greece. Although the disease had not then appeared in Greece, the pathologists there would like to be ready for it when it does come.

_Pollinations in 1946 and 1947._ Without going into details, the general purpose of the pollinations during these last two years has been to incorporate more and more of the resistant Chinese stock into our hybrids. Beginning in 1937, we crossed our best Japanese-American hybrids with Chinese, and we now have a considerable number of young saplings of flowering age, which have the pedigree: Chinese x Japanese-American. Unfortunately, in this cross the Chinese is usually dominant as regards habit, but not always. We have some tall, straight-growing individuals of this combination which may well be the forerunners of a blight-resistant forest stock for America.

Therefore, during 1946 and 1947 we have been crossing these fine Chinese x (Japanese-Americans) with the following:

1. Our best Chinese
2. American-Chinese and Chinese-American
3. American (C. dentata)
4. Our best Japanese-Americans
5. Among themselves

For it is the ultimate aim of this work to develop a race of tall, hardy, blight resistant individuals which will breed true and thus of themselves re-establish the chestnut tree in the forests of Eastern North America. As everyone knows, the re-establishment of the chestnut as a forest tree can not be done in a few years or even a score of years, but by continued breeding and patience and perseverance it can be done. The materials are at hand, i.e. tall, erect growth, and blight resistance; and with persistent effort the desired combination can be made.

For (1) above we were fortunate in 1946 in receiving a supply of pollen from tall-growing Chinese trees, through the kindness of Mr. Michael Evans of Greenville, Delaware and Professor Maurice A. Blake of the New Jersey Agricultural Experiment Station.

As a result of our pollinations in 1946, in which 72 combinations were made, we harvested and planted in our cold frames in October 479 hybrid nuts, a large proportion of which germinated, so that this summer (1947) we have set out in our nurseries about 325 hybrid seedlings.

In 1947 we have made 58 combinations in which 213 branches were bagged; October 10-13 we gathered 380 hybrid nuts resulting from these cross pollinations. The large yield of 1947 is doubtless the result in part of a good growing season, for there was plenty of rain--at times almost too much--in southern Connecticut. One drawback was the cold period during the latter part of June. From the fifteenth to the twenty-sixth the minimum temperatures were 55 or below--on three days as low as 50. This set back the flowering period four days to a week later than usual, depending upon the species or hybrid.

_Cooperation in Diller's Underplanting and Girdling Method for the Establishment of Chestnut Forest Stands._ In the 37th Annual Report of our Association for 1946 is printed a paper by Dr. Jesse D. Diller of the Division of Forest Pathology, U.S.D.A. entitled "Growing Chestnuts for Timber" pp. 66-68. Many people seem to think that all you need to do when planting a tree is to stick it in the ground--just _any_ ground. This may be true of some kinds, but is certainly not true of the chestnut. For best growth and development the chestnut requires a fairly deep, well-drained soil, rich in mineral elements and humus, with a fair degree of moisture and plenty of sunlight. Two things chestnuts will _not_ endure are shallow soil and drought, the latter often depending on the former.

As tree indicators of the kind of site required for the establishment of a chestnut forest Dr. Diller has chosen yellow poplar, northern red oak, white ash, sugar maple, and yellow birch, with spice bush as a shrub indicator and maiden hair fern, bloodroot and other herbs as herbaceous indicators. Using a small area of about one eighth of an acre, Dr. Diller's plan is to girdle all the trees and then underplant with chestnut seedlings. He says: "As the girdled overstory trees die they gradually yield the site to the planted chestnuts in a transition that does not greatly disturb the ecological conditions, particularly of the forest floor. Rapid disintegration of the mantle of leaf mold is prevented by the partial shading which the dead or dying overstory, girdled trees cast." This may seem to some a rather drastic method, but when so much is at stake, namely the re-establishment of the chestnut in our forests, it would seem a justifiable experiment on a small area.

In March, 1947, we supplied Dr. Diller with one hundred seedlings, one or two years old, of our best stock, for underplanting in two of these selected sites, fifty seedlings each, namely on the estate of Mr. E. C. Childs at Norfolk, Connecticut, and on lands of the T. V. A. at Norris, Tennessee. Our best wishes for a successful blight-resistant future go with these little trees.

_Grafting Work._ We are continuing with our method of "inarching" young "suckers" from below a blighted area into the trunk above the lesion, the diseased tissue of the lesion being first cut out. This method (see Brooklyn Botanic Garden Chestnut Breeding Project. 35th Annual Report of Northern Nut Growers Association for 1945. pp. 22-31--1945) is entirely successful in case we desire to preserve partly resistant hybrids of good parentage for future breeding and for scions. (Figs. 1 and 2) But inarching of the native chestnut is for the most part unsuccessful because the fungus grows too rapidly and girdles the stem, killing the parts above before the inarched tips of the suckers can take hold. There seems to be a certain relation between the amount of disease resistance in the tree and the possibility of restoring it to health by the inarching method.

By the common ordinary cleft-graft method, using Japanese, or better, Chinese stock we are adding to the supply of our most desirable hybrids.

_Insect Pests._ The spring canker worm, _Paleacrita vernata_, has not been destructive either in 1946 or 1947 and no special preventive measures have been taken. Japanese beetles have done a little damage. This year the first one appeared July 11. We find the best method with these is to pick them off at dusk after they have settled themselves for a night's sleep, dropping them into kerosene oil. Under these conditions they will usually slip readily off the leaf into the oil. One thing I should like to emphasize (which probably others also have noticed) is that new beetles keep coming, day after day. Apparently the adults are issuing from the ground all summer. Last year I found a few Japanese beetles in November. So one must keep continually on the job all through the season. This summer (1947) we have had a spray program of three sprayings, August 15, 30, and September 10, with "Deenate" (fifty percent DDT) to destroy the chestnut weevils which appeared for the first time rather extensively in our Hamden plantations last year. (See E. R. Leeuwen; DDT for chestnut weevils, American Fruit Grower 67: 28. 1946) This spray, which we have used on the ground as well as on the young burs, kills Japanese beetles as well as the weevils. This fall I have seen very few weevils in our whole crop of nuts.