Part 10

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.