Pecans.Posey and Greenriver are given top mention for hardiness, with Busseron, Major, and Niblack next. In the more southern areas, of course, the more tender varieties are favored, such as Mahan, Success, Burchett, Schley and Stuart. Mahan seems to be the one most favored for general excellence in yield, flavor, and cracking qualities. It must be said, however, that, in flavor, these larger pecans are inferior to the best pecans of the indigenous northern varieties which are now being propagated. But because of their size, beauty, and productiveness, they will probably maintain their present leadership commercially.
Hybrid Pecans, Filberts, Butternuts.Reports from the south are inadequate for appraisal. The inference one must draw is that they are not being planted extensively there.
Persian Walnuts.The object of the inquiry, of course, was primarily to get information about varieties which might be capable of expanding their range toward the north. In this, so far as the southern reports are concerned, we have not been successful. Placentia and Eureka are mentioned in one report but their records, as reported, are not particularly good. Corroborative evidence is needed. Upon the whole, the south, strangely enough, seems not to be the place to look for Persian walnuts for the north. In California, the varieties of Persians, Juglans regia L., are well rooted to the ground. They object to more northern locations. This may not be entirely true of another species, J. hindsii, which in the past has shown a tendency to cross with other members of the juglans tribe. Crossed with the native black walnut, the hybrid known as "Royal" was developed, a robust grower which bears little. Crossed with the Persian, "Paradox" was produced. We are indebted to Mr. Harry S. Welby, of Taft, Calif., for some interesting J. hindsii varieties of good size and rather large, well filled kernel capacity. Upon their exterior, the nuts resemble the Persians, and the kernel has the Persian flavor. Inside the shell, the structure is that of the American black, with a substantial woody cross-brace, and the shell itself calls for a hammer for cracking. Neither Paradox nor Royal have proved of value except for stocks upon which the growers graft or bud their commercial cions. Much experimenting has been done in hybridizing J. hindsii, thus far without producing more than comparatively sterile "mules", but, the tendency to cross having been demonstrated, this work should be continued. Mr. Welby's samples have been sent to Mr. C. A. Reed, at the Beltsville Experiment Station, for evaluation. "Perhaps someone will know," says Mr. Welby, "the limit of cold J. hindsii will stand."
Mr. Welby's comments accompanying his report are too interesting to omit. He says: "On the grounds of an oilfield camp, I have carried on collaboration with the U. S. D. A. Bureau of Plant Introduction for twentyyears. The importation of graftwood of eastern soft shell black walnuts has been "on my own." Of black walnuts we have bearing trees among ornamental plantings. There has been a marked change of attitude from the early days when I was more or less looked upon as a freak for working with them. The nuts are valued today. The original objective has been attained.
"In the meantime, I have purchased, 450 miles north of here, a twenty; have fenced and planted it to a brand of permanent pasture grasses known as "Evergreen", furnished by a grass specialist, Dale Butler, of Fresno. Prior to the grass, black walnuts, grafted and ungrafted had gone in. A strip bordering the highway was reserved for trees, we hope pistachio. There are now thirty of that variety, bearing, in an interior block.
"We have for years purchased black walnut meats in the Chico area. That would be a paradise for a black walnut man. And years ago I visited Teharna, a deserted village from the storybook, a former pony express station—wonderful black walnuts! Upon placing my camera upon a stump of a tree that grew in the street-parking, which had been logged, I braced the camera with a chip of this four-foot stump and discovered that the tree had been a curly walnut. The trees there are notJ. hindsii, but Missouri blacks planted by forty-niners.
"Concerning pistachio: I doubt, considering the percentage of members who would be interested, whether I should bring this up, but there is need for just such an organization as the N. N. G. A. behind this tree. It does not lend itself to common nursery practice. It should be raised from seed, potted or in cans, reared without babying for several years, a horticulturist brought in, and your pistachio vera male and female blossoms worked toP. atlanticaorchinensis. Lots of work but it is worth the trouble. It is deciduous with a hickory-like foliage; clusters of nuts clothed in pink-cheeked hulls. Bailey reports best nuts come from Sicily. Perhaps knowledge of them will be more widely disseminated when the boys return."
Hickories.This species seems not to be of great interest to the south. The old varieties are not mentioned in the reports. Nugget is mentioned by Mr. W. D. Dockery, of Steele, Ala., as one of the best. It grows well, yields well, its kernels have a good size and their quality is unusually good.
Ofheartnuts, only one is mentioned, the Lancaster, which leaves much to be desired in performance in the south.
Suggestions and Requests.In response to the questions, "Is there any service that N. N. G. A. could render you not now being met?" and "Have you any suggestions for future work?", a number of responses were received which are worth noting.
Dr. O. D. Diller, State Exper. Sta., Wooster, O., "We are thinking in terms of another state wide nut contest in the fall of 1944." It will be remembered that the last Ohio contest brought the Brown and Tritton trees to light. Both are making friends by good production of good nuts. This is a suggestion for promotion in other states.
Sylvester Shessler, Genoa, O.: "Planted 10 nuts from Tritton parent tree in 1935. One seedling bore a larger nut than the parent tree. Several others bore very small nuts but all well filled."
J. Russell Smith, Swarthmore, Pa., "Urge the members to run local contests for good nuts. It may bring members if not nuts, and you may find some good new neighbors you didn't know about." (One easily worked plan is to see the secretary of your county fair board, offer to pay half or all prize money for best nuts from a single tree in your own and surrounding counties. See that judging is done by someone who knows how or do it yourself.)
Alfred J. Frueh, W. Cornwall, Conn., "Have had quite a lot of winter injury on the south-west side of black walnut trunks grafted near the ground. Note that seedling walnuts have a ridged, corky bark on the trunk already the second year, whereas a grafted trunk maintains its smooth bark for 6 to 8 years. Am now grafting on seedling stock 5 to 6 feet above the ground and much of the winter injury is thus eliminated."
A. B. Anthony, Sterling, Ill., "If they can be had disease free, promote the planting of a few of the most choice chestnuts in widely scattered regions where no one grows such trees. Possibly our children can get back to chestnut growing."
Seward Berhow, Huxley, Ia., "In a separate (pamphlet) or included in an early report, give a complete list of all named varieties, especially black walnuts, name of nut, name and address of originator, location of original tree, north latitude, year discovered, nuts per pound, score for cracking, kernel, prizes won. This would be very valuable for quick reference." The T. V. A. has issued a pamphlet giving much of this information. Also, we believe, Mr. C. A. Reed is at work on a book which will be worth waiting for.
J. U. Gellatly, Westbank, B. C.: "Could not the Association supply samples of recommended nuts or perhaps give lists of those who would sell small (3 or 4) nut samples. I have sent out such samples of 2 or 3 each of varieties I have on hand up to 9 or 12 kinds, at 50 cents per package, post paid. This is not enough to pay for the time consumed but is a good advertising practice."
Harry S. Welby, Taft, Calif.: "The ground squirrel is a pest here. Black walnut as bait will attract them in winter when fruits are scarce. At that time I have had some success with a box trap treadled by an electric contrivance instead of figure 4. Can anyone tell me any experience with scent baits which I believe Biological Survey trappers sometimes use? It may be a delicate question, but I should be interested in knowing more if the information is available."
R. T. Dunstan, Greensboro College, Greensboro, N. C.: "I would be happy if this survey brings to light information on the behavior of the best and more recently discovered hickories. (If not,) I believe an article on performance of such varieties as Whitney, Grainger, Bergor, Davis, Wilcox, Schinnerling, etc., perhaps similar to that by Reed in 1938 Proceedings, would be highly valuable and welcome. Perhaps a report on T. V. A.'s nut tree work in recent years would also be worth while."
C. H. Parks, Asheville, N. C.: "Would be interested in a chestnut that will grow in southern Appalachian regions." (See Mr. H. F. Stoke's report above. Chairman.)
Harold G. Williams, Ramsey, N. J.: "I believe that most useful trees, both fruit and nut, that are now commercially important, were developed from selected seedlings grown in the area in which they are being used. I have a suggestion. How about a concerted breeding program for nut trees with full membership participation? The best parent trees should be selected from present plantings of grafted, named varieties. Ship these seeds, or one or two year old seedlings from them, to each member on a subscription basis. Let each member make a trial planting of as many trees as he can. When these trees come into bearing there will be a better chance of finding superior strains that are adapted to their environment. Hybridizing by cross pollination requires more time and skill than many of our members possess. There are, however, members who now own orchards containing some of the best varieties, such, for instance (among the black walnuts) as Thomas, Stabler, Stambaugh, and perhaps Elmer Myers, planted in such close proximity as to allow for cross pollination. Seed could be purchased from them and resold to members for their planting; costs to be kept fairly low, with annual reports required as to care, cultivation, fertilizing and growth.
"An alternate plan would be to turn over such seed to Hershey, Smith, and other member nurserymen to plant, grow the young seedlings under best conditions, and furnish to member cooperators whose pledged subscriptions are to take care of the cost. This would give the cooperating nurseries a piece of business that could be depended upon (of a kind that would take comparatively little time as compared with that required for grafted trees), in return for their support. These trees could be planted fairly close, since most of them would prove to be useless as nut producers. If an outstanding variety is found, everything around it should be chopped down to give it room for development. I personally would raise and report upon some two dozen trees of this kind, and if a large group joined in the work, hundreds of tree could be tested."
Comment: That the chairman of this committee thinks the above suggestion a good one, and the project a good gamble, is evidenced by the fact that he has about a thousand of such trees now growing. Seed was bought from Mr. Harry Weber's, Rockport, Ind., and Mr. C. F. Hostetter's Bird-in-Hand, Pa., plantations in the fall of 1937 and planted at once. Most of the seed was from Thomas trees which had been flanked in the plantations with Stablers and other named trees, and from Stablers similarly flanked. The trees have now had six years' growth. He hopes for first nuts in 1944from seedlings planted in deep loam only. Growth elsewhere has been negligible. If no outstanding nut producers are found, there will at least be some splendid timber, already assured.
It should be stated at once, however, that those whose object is the assured production of nuts, rather than the discovery or development of a new variety, should never plant anything but the best grafted trees bought from reliable nurserymen. Your decision should be governed by your interest. If you wish to be sure of nuts of a certain quality for home use, buy grafted trees of that quality. If, on the other hand, you have the urge to probe into the unknown and possibly create a new type, the above project will appeal to you, especially if you should lack training and time for more painstaking work. The following account is an example of the latter kind.
Arthur H. Graves, Curator, Brooklyn Botanic Garden, says: "We are breeding chestnuts for the purpose of obtaining a disease-resistant timber tree stock similar to the old chestnut tree which has now nearly disappeared on account of the blight. We started breeding chestnuts here at the Botanic Garden in 1930, and now after thirteen years of work, have on our plantation at Hamden, Conn., Litchfield, Conn., where the White Memorial Foundation is cooperating with us, and Redding Ridge, Conn., where Mr. Archer M. Huntington and the Connecticut Agr. Exp't Station are cooperating, about 1000 hybrids, a large number of combinations of Chinese, Japanese and American chestnuts, many of them now in the third generation from the beginning of the breeding period in 1930.
"We are carrying out our breeding program in the following way:
"We have selected the Chinese and Japanese species to cross with the American because the Asiatic species are disease-resistant, and we hope to incorporate this quality of disease-resistance with the tall timber growth of the American. We find that the Chinese are in general more disease-resistant than the Japanese. Other stocks which have been incorporated in our hybrids are the EuropeanC. sativa, the southern chinquapinsC. pumilia,C. ozarkensis,C. floridana, and Dr. Van Fleet's old hybrid, presumably ofC. crenataandC. pumila, which goes under the name of S8, andC. seguinii. After the hybrids become old enough, we inoculate the tallest of them with the blight fungus in order to get an index of their disease resistance. The most disease-resistant are bred together and of their offspring the tallest are selected, inoculated, and the most disease-resistant are bred together again. For example, this year we had 350 hybrids from last year's breeding experiments set out in a special nursery at Hamden and carefully tended during the season. Of these 350 we have selected 50 which are the tallest and straightest, that is, 20 inches and over. The others were sent to Washington, D. C., where the Division of Forest Pathology, Department of Agriculture, is working along a similar line, but with more attention to the nut phase of the problem.
"Our ultimate aim, of course, is to establish a race of chestnut trees which shall replace our now practically extinct American chestnut. The loss in money value from this timber tree has amounted to millions of dollars in comparison with which the value of its nut crops is very small indeed.
"However, we are interested in the nut problem, and whenever any particularly fine nuts appear we note the fact. We have now a strain of Chinese chestnut which has not yet come into bearing which we believe will have nuts as sweet as the old American chestnut, but much larger."
With this forward-looking note we close our report. We have a foundation upon which to build that is substantial and tried. The pioneering work of a patient, far-sighted, and distinguished group of workers has shown us much of what to do and what not to do. It is now up to us, the farmers, the planters, to multiply their work and continue it.
Very many interesting bits of information have been included in the survey reports; so many that the committee has regretfully omitted some that hardly seemed properly to belong with the material of a survey, which after all must have some limits. One such item is from J. C. McDaniel, of Haines City, Fla., and has a special interest for members of this Association. He says:
"Perhaps you will be interested in data on one of America's largest Chinese chestnut trees, even if it does grow in Florida, at Monticello. It stands adjacent to a lot in which the late J. F. Jones had a nursery for a short time in the early years of this century, and apparently was planted at that time, around forty years ago. The trunk is now more than 25 inches in diameter below where it divides 6 feet above the ground. From this level, the tree branches profusely and has a symmetrical, rounded crown. It is healthy, not having a sign of the bark disease, although a native chinkapin 100 feet away is badly infested. It has abundant bloom and sets heavy crops of burrs but, lacking another variety for pollination, the number of nuts matured is small. Nuts are about average size for the species, of typical sweet flavor, and separate readily from the pellicle. Many of them become infested, before ripening, with a fungus which rots the kernel, apparently the same one which infests chestnuts and chinkapins at Savannah and Albany, Georgia. Mr. Paul Goldberg, of Monticello, the present owner, states that the tree has been bearing annually during the twenty years his family has owned it."
This nut-rot among the oriental chestnuts is one of the diseases that have become troublesome elsewhere. It is being studied and efforts are being made to combat it. Thus far, so far as we know, no effective cure has been found. A report upon present progress would be worth while.
Oscar E. Swan, Jr., Tulsa, Okla., reports an enviable situation. He says: "My nut trees are growing on a farm where more than 30 years of cultivation have failed to kill the native pecan sprouts. They come up year after year from the top roots. Since acquiring the place in 1936, I have allowed the pecan sprouts and the few native walnuts to grow unchecked except where necessary to cut them out to avoid crowding. The growth of these sprouts is quite vigorous, and they are ideal for top-working. I have top-worked a few trees every spring and now have about 300 grafted trees all the way from 6 to 30 feet tall. Many are too close together for full grown trees and I plan to thin them. My problems, so far, are the mechanical ones of top-working. I have settled upon a modification of the Biederman bark graft, which gives very good results. After the grafts are well established, the trees get very little attention except for cutting out the crowding trees. They are literally growing 'wild', yet the growth has been better than transplanted trees would have made with the best of care, because the root systems are well established in a situation which suits them.
"This system of neglect probably explains why I have failed with some species and varieties such as the butternut and some of the hickories. Occasionally I am pleasantly surprised, as in the case of some seedling Carpathian walnuts which, grafted upon some established black walnut sprouts, came through the severe 1943 drouth in fine shape withoutbenefit of mulch, cultivation, fertilizer, or watering. The same applies to the Helmick hybrid. (A two year old tree, a hybrid walnut, grafted and growing well on black walnut stock, and which Mr. Swan says will bloom next year.) I have pampered my Chinese chestnut trees with cultivation, mulch and manure, as they are located in poorer, drier soil. They were badly hit by the drouth. Some died in spite of the attention.
"As to varieties, I am far enough south to grow all the standard southern pecan varieties, although several do not have a long enough season to mature their nuts. I am trying the northern varieties and, so far, am well pleased with their growth as compared with the southern kinds. It will be a few years before I can report on the size and quality of their nuts."
J. C. McDaniel again: "Source and variety of seed in Chinese chestnuts have a great influence on the performance of seedlings. Numerous seedlings from the original Hobson tree began fruiting in their second season of growth, and half of the ones I have are fruiting during their fourth season. On the other hand, I have a tree from imported seed which grew nine seasons before setting and ripening its first burr. The above data refer to my planting near Hartselle, Morgan County, Ala., and that vicinity. I have several black walnut trees under observation, native trees, on which data are not yet complete enough for evaluation."
If any man deserves a bright N. N. G. A. medal, it is A. L. Young, of Brooks, Alberta. Lowest temperature expected in winter, 45° below; lowest known, 62° below. Highest expected in summer, 101°. Frequent drouths? Yes. Hot, dry winds? Yes. Native nuts found plentifully? None. Sparingly? None. Yet Mr. Young plants nut trees. It is men like that who have made Canada what it is. It takes more than mere weather to stop them. The never-say-die spirit of pioneers speaks throughout his report:
"Black walnuts, butternuts, some oaks, hazels and American chestnuts (Ohio buckeyes) all came through last winter well. However, late frosts reduced the nut crop. Of these species, filberts are not getting anywhere. Winkler, I believe, will eventually make a go of it. Heartnuts got a rough deal last winter, and European buckeye chestnuts were hurt a little by late spring frosts. Some Manchurian walnuts also got a setback with spring frosts, and some did not. Carpathian walnuts killed back quite a lot, so did most of my hybrid walnuts. Hybrid hazels seem perfectly hardy. Pecans, beechnuts and sweet chestnuts almost passed out of the picture last winter. Giant hickory from Ontario seems hardy but particular about the kind of soil and conditions. When irrigated, too much water will kill them. And this is true also of walnut and butternut seedlings. I have no acreage of nut trees. I grow seedlings and plant them wherever I find a place protected from the stock and within reach of moisture from the irrigation ditch, as this is a desert, cactus country.
"I always have a stock of seedling trees on hand, and whenever visitors show any interest, I give or send them fruit or nut trees and a few perennial flowers. So there are sure to be a few nut trees, some day, growing successfully throughout Alberta.
"There is more benefit from this northern seed, especially as I am using a commercial pollen with the hope of getting a hardy white walnut with possibly a coarse bark like the black to ward off sun-scald in this climate. They are on their way. I don't know when we'll be eating these imaginary nuts. However, it is not so long ago that fruit growing on the cattle range was a dream. I grew the first pears in Alberta, so far as we know. Now we are insulted if there is not a crop of fruit every year. I have many seedlings of standard apples, unnamed, that are really choice fruit, and, of course, a few named varieties that are doing fairly well. Minnesota has done great work in apple and plum breeding for the north. We are enjoying some of them right here.
"I am sorry that I have no data on husking, cracking, etc. Really even the hardiest, best trees bear nuts that, while of fair size, do not have fleshy kernels, and some have three sections instead of two. Butternuts are very sweet with fair size kernels. I was surprised, after a long hard winter, to find the Ginkgo trees still alive and gaining growth. Credit some or all this result to J. U. Gellatly and Paul Crath for supplying me with seed, seedlings, and pollen to carry on with. I am greatly obliged to them and also to George Corsan of Echo Valley, Islington, who has a wealth of nut interest.
"We have had a mighty dry year here, so, between irrigating and tending the largest herd of Ayrshire cattle in the prairie provinces, I have been busy. The town of Brooks is probably the only town in Canada on straight Ayrshire milk; and the change in Brooks from a box-car on a siding years ago to the Brooks of today, with its hundreds of healthy children now on the streets, is the marvel of a man's lifetime."
George H. Corsan, Echo Valley, Islington, Ont.: "Last winter, 1942-43, was by far the coldest ever recorded. No damage to filberts. A few inches of twigs were hurt on certain English walnuts. The Stranger heartnut, a tender variety, passed through unscathed. Persimmons and pawpaws passed without a bud killed. These are perfectly hardy varieties. Jujubes passed O. K., but that may be due to the very deep snows."
Dr. Oliver D. Diller, Associate Forester, Ohio Experiment Sta., Wooster, Ohio: "You will be glad to know that the experiment station has set aside some land for improved varieties of nut trees. If you find some promising walnuts which might be tested in this part of the state, we should be glad to have you keep us in mind." This is indeed welcome news and will be appreciated by all growers in this area.
J. G. Duis, Shattuc, Ill.: "A chicken yard is one of the best places to grow nut trees."
J. U. Gellatly: "I do not believe in selling nuts for seed purposes except on a very large scale."
J. C. McDaniel: "A neighbor lost some 5 year old Chinese chestnut trees following a summer drouth on silty loam soil, rather shallow to hard-pan. It is my observation that deeper, sandier soils (not too extremely sandy) are best for chestnuts in the coastal plain and other regions subject to summer drouths. In the mountains where summer rainfall is more uniform, they thrive also in clay soils."
G. H. Corsan: "Best success in grafting (hickories) has been in juicy, wet springs. Heartnuts must not be budded until late August (in Islington, Ontario). Heartnuts must not be pruned."
A. L. Young, Alberta: "There is a demand for young walnuts for pickling." (Does anyone know the details—when to pick, how to pickle?) (Note by Ed. Several recipes and methods in Am. Nut Journal now out of print but indexed by Ed. Copies of this index in his hands and those of Mr. C. A. Reed at Washington. Also recipes in 33rd Ann. Report p. 95).
Sterling A. Smith, Vermillon, O.: "With me, summer budding is the most successful means of propagating black walnuts."
J. Russell Smith: "Chinese chestnuts will blight some if under-nourished." Which includes the wrong kinds of soil, if uncorrected.
"Does anyone know for sure how to get pawpaw seed to germinate?" Several have asked this question. The chairman has had the same trouble, so can not answer. (Note by Ed. See "Nut Puttering in an Offyear" in this report.)
So far as the correspondence shows, no state or federal department buys seed on a large scale (with the exception, now, of chestnut seed) from trees of the better named varieties with which to grow seedlings for distribution by state nurseries for forest planting. All nut seed seems to be gathered haphazardly.
W. G. Tatum, Lebanon, Ky.: "A nut tree with plenty of root, top cut back one third, promptly set, roots protected, stem wrapped, 4 inches, mulch applied, set either spring or fall, grows for me 99% of the time. Failures are not worth mentioning if the above conditions are met."
Carl Weschcke, St. Paul, has a dozen or so extra hardy Persian walnuts by selection from some 12,000 seedlings. Also is introducing the hardy "Hazelbert," result of crosses between wild varieties and filberts.
"Dip wire screen guards in red lead and they will be good for twenty years."
Thomas and Stambaugh, among the black walnuts, are, with justice, entrenched leaders, but it will be well to watch Patterson, Mintle, Elmer Myers, Eureka, Creitz, Todd, and other promising new ones less well known. Thomas is more prolific in the south (generally) than in the north, which indicates that its bloom may possibly be out nearly enough to suffer in the north from late frosts.
Among chestnuts, the weight of evidence favors Hobson, Carr and Reliable, though J. Russell Smith says he has something he likes better than the first two.
Among pecans, Major, Greenriver, Pleas; among filberts and hazels, Winkler, Jones hybrid, Cosford, Gellatly, Brixnut; among Persian walnuts, Broadview, one or two Crath varieties, Payne, Breslau; among hickories, Stratford, Fairbanks, Barnes, Glover, Weschcke. These seem, so far as the returns show, to have outstanding points of superiority. In any such survey, injustice is bound to be done to some not fully reported.
Outside of filberts in the northwest, no northern grown nut can yet be said to have reached the status of a profitable commercial crop. (Exception: The narrow pecan belt along the southern terminus of the Ohio river valley; mostly wild trees.) Dr. A. S. Colby, University of Illinois says, "The report from the State Statistician at Springfield indicated a crop of 575,000 pounds of pecans for Illinois in 1943. I don't know just where they came from." Short crops were reported in Calhoun and Gallatin, leading nut producing counties. No reports have been received as to the size of pecan crops in the Kentucky and southern Indiana portions of the same belt.
The search for better varieties must continue, but it is also altogether likely that with an orchardist's attention, with cultivation, mulching, fertilizing, spraying one to three times yearly with Bordeaux and lead sprays, we might approach the commercial goal more closely with what we have today. Is anyone treating a bearing nut orchard as well as he would treat an apple orchard? That's the test.
S. H. Graham of Ithaca, N. Y. says: "The Ohio is commonly regarded as hard to hull. With a chained tire husker it hulls as well as any." He rates it for hardiness and a percentage of 90 to 100 for filled nuts, while Thomas yields only 0 to 90%.
Seasonal ZonesSeasonal Zones Compiled from the U.S. Department of Agriculture Records, Based on the Average Date of the Last Killing Frost in Spring
The problem of walnut toxicity dates back at least to the writings of Pliny. In his "Natural History," this Roman philosopher stated that "the shadow of walnut trees is poison to all plants within its compass" and that it kills whatever it touches.
The first rebuttal to the existence of such a toxicity was forwarded by Evelyn in the 17th century. This author discussed the high regard in which walnuts were held in Burgundy as field trees. The roots of these trees were below the plow sole and thus did not affect either cultivation nor the growth, of grasses and cereals beneath them.
The pros and cons of the problem have been reviewed several times in the recent proceedings of the Northern Nut Growers Association. (Greene, 1930; MacDaniels and Muenscher, 1942; Brown, 1943.) That the roots of walnut trees are toxic to the roots of certain crop plants in direct contact with them is widely accepted. In nature this toxicity seems to be limited to plants with tap root systems such as tomato and alfalfa (Davis, 1923) and those with other types of deep root systems such as apple trees (Schneiderhan, 1927), rhododendrons (Pirone, 1938), and privet. This toxicity is exhibited only when there is a direct contact between the roots of the two plants involved. (Jones, 1903; Massey, 1925). That the wilting observed under walnuts is due to a toxic product from the bark of the walnut, and does not result from a lack of water, is substantiated by the fact that the vascular or water conducting system is discolored for several inches above the point of contact with the walnut root. This symptom is very similar to that produced by vascular disease fungi. No such discoloration results from wilting due to competition for water. This symptom of toxicity has been overlooked by many workers in the field.
Massey (1925) suggested that the toxic component of walnuts might be juglone. This idea was further supported by Davis (1928). Today this concept is widely held. Chemically this substance is known as 5, hydroxy-1, 4, naphtho-quinone and belongs to a group of strong oxidizing agents with commercial uses, including tanning agents, medicinals, poisons, etc.
A knowledge of the physiology of juglone in the walnut is essential to an understanding of the divergent results obtained by various experimenters. Juglone, as such, occurs probably only in minute quantities in the inner root bark, and in the green husks of the nuts. These regions are, however, rich in a substance known as hydrojuglone. This compound, the colorless, non-toxic, reduced form of juglone is immediately oxidized to its toxic form upon exposure to the air or some oxidizing substance from the roots of other plants. Upon standing in the air juglone again disappears, being either changed back to hydrojuglone or broken down into other non-toxic substances.
This sequence of events may be noted in a fresh green husk of a black walnut. When the fresh husk is cut, the interior is white but immediately turns yellow as the colorless hydrojuglone is transformed into the yellow juglone. Upon standing or drying the husk becomes black as further chemical changes occur. It is impossible to extract juglone from these dried husks without first reoxidizing them.
It now becomes possible for us to understand some of the discrepancies in the studies on walnut toxicity. If walnut bark or other plant parts are allowed to become desiccated, no toxicity may be found. If the roots of plants do not contact plant parts containing juglone or hydrojuglone, their oxidizing ability can not produce the toxin. Further the relative amounts of juglone in various species ofJuglanshas not been completely investigated. It does occur definitely inJ. nigraandJ. cinereaand has been reported as being inJ. regia. Other species need investigation before being included as sources of juglone.
It is known that many plants are not adversely affected when grown under or near walnut trees. Some of these have root systems too shallow to contact the roots of the walnuts, especially in plowed ground. Some plants may send out sufficient surface roots to keep the plant alive in spite of injury to the deeper roots. The possibility that the roots of some plants are capable of withstanding the oxidizing power of the juglone is currently under study.
In early American folklore, the inner bark and the husks of the nuts were used as a source of a yellow dye for cloth. This yellow dye is juglone. The ancients also used this method of dying both cloth and hair.
Another property of juglone is its toxicity to fish. A few years ago it was a common practice in the South to cut the husks from young nuts and throw them immediately into a still pond of water. The fish, stunned by the juglone, would rise to the surface and were collected and eaten. No one seemed to worry about the effects of such poisoned food on the consumers.
Juglone is toxic to fungi and bacteria. Of all the medicinal powers attributed to walnuts by the Greeks and Romans, its use in curing certain skin diseases including ringworm has held up through the ages until many today can recall the use of the green husks for control of ringworms. Brissemoret and Michaud (1917) reported the use of juglone in clinical cases for the cure of eczema, psoriasis, impetigo and other skin diseases and concluded that juglone deserves extensive use in dermatology. To our knowledge the medical profession has not followed up the possibilities which this substance offers. The author is familiar with one case in which pure juglone was applied to a persistent ringworm infection. The infection disappeared within a month after treatment was begun. Though conclusions can not be drawn on a single case, certainly this observation lends credence to the medicinal lore of the ancients and the American pioneers.
During the fall and winter of 1942-43, investigations on juglone were started at the Connecticut Agricultural Experiment Station in conjunction with studies of the effect of other plant toxins on the roots of higher plants. When the toxicity of this oxidizing compound was established, it was produced in some quantity both by extraction from walnuts after the method of Combes (1907) and by synthesis after the method of Bernthsen and Semper (1887). Working on the assumption that the killing of germinating fungus spores and root hairs are similar phenomena, juglone was subjected to standardized laboratory tests for fungicidal value. In a series of experiments, this compound proved to be equally toxic with the copper in Bordeaux mixture. Such a high degree of toxicity was deemed worth further investigation, so juglone was tested as a seed protectant and as a spray in field trials for the control of black spot of roses.
As a seed protectant, juglone failed miserably. It's toxicity to the noncutinized surfaces of root tissues was so great that germination was abnormal and greatly impaired. The injury noted here was apparently the same as that discussed by Brown (1943) and that which occurs normally in the field.
In field tests on the control of black spot of roses juglone stood up well. No phytotoxic activity could be noted on the cutinized stem and leaf surfaces. On the variety George Ahrens, juglone gave equal control with 2½ times as much 325 mesh sulfur, the standard control for this disease.
1. Under certain conditions walnut trees exhibit toxicity to those plants whose roots are in intimate contact with the roots of the walnut.
2. This toxicity is due to the action of juglone, the oxidized form of hydrojuglone, a non-toxic substance occurring in the inner bark and green husk of walnuts.
3. Juglone has been used in dermatology to cure various skin disorders including both bacterial and fungus diseases.
4. As a seed protectant, juglone is unsuitable because of its inherent toxicity to the non-cutinzed root surfaces.
5. Laboratory and field tests have shown juglone to be an excellent fungicide
1. Bernthsen, A. and A. Semper Ueber die Constitution des Juglons und seine Synthese aus Naphtalin. Ber. d. deutsch. Chem. Gesellsch. 20: 934-941. 1887.2. Brissemoret et Michaud Sur une nouvelle classe de médicaments de la peau; les quinones peroxydes. Jour. pharm. et chim. 7e ser. 16:283-285. 1917.3. Brown, Babette I. Injurious influence of bark of black walnut on seedlings of tomato and alfalfa. Northern Nut Growers' Assn., Proc. 1942:97-102. 1943,4. Combes, R. Sur un procéde de preparation et de purification des dérivés oxyanthraquinoniques et oxynapthoquinoniques en genéral, du juglon et de l'émodine en particulier. Bull. soc. chim. 4c ser. 1: 800-816. 1907.5. Cook, Mel T. Wilting caused by walnut trees. Phytopathology 11:346. 1921.6. Davis, Everett. The toxic principle ofJuglans nigraas identified with synthetic juglone, and its toxic effects on tomato and alfalfa plants. Amer. Jour. Bot. 15: 620. 1928.7. Greene, K.W. The toxic (?) effect of the black walnut: Northern Nut Growers' Assn., Proc. 1929: 152-156. 1930.8. Jones, L. R. and W. J. Morse The shrubby cinquefoil as a weed. 16th Ann. Rpt, Vt, Agr. Expt. Sta. 188-190. 1902-03.9. MacDaniels, L. H. and W. C. Muenscher Black walnut toxicity. Northern Nut Growers' Assn., Proc. 1940 172-179. 1941.10. Massey, A. B. Antagonism of the walnuts (Juglans nigra I.andJ. cinerea.) in certain plant associations. Phytopathology 15: 773-784. 1925.11. Pirone, P. P. The detrimental effect of walnut to Rhododendrons and other ornamentals. Nursery Disease Notes 11; 1-4. 1938.12. Plinius Secundus, C. The historie of the world. English translation by P. Holland, A. Islip, London. 1601.13. Schneiderhan, F. J. The black walnut (Juglans nigra L.) as a cause of death to apple trees. Phytopathology 17: 529-540. 1927.
1. Bernthsen, A. and A. Semper Ueber die Constitution des Juglons und seine Synthese aus Naphtalin. Ber. d. deutsch. Chem. Gesellsch. 20: 934-941. 1887.
2. Brissemoret et Michaud Sur une nouvelle classe de médicaments de la peau; les quinones peroxydes. Jour. pharm. et chim. 7e ser. 16:283-285. 1917.
3. Brown, Babette I. Injurious influence of bark of black walnut on seedlings of tomato and alfalfa. Northern Nut Growers' Assn., Proc. 1942:97-102. 1943,
4. Combes, R. Sur un procéde de preparation et de purification des dérivés oxyanthraquinoniques et oxynapthoquinoniques en genéral, du juglon et de l'émodine en particulier. Bull. soc. chim. 4c ser. 1: 800-816. 1907.
5. Cook, Mel T. Wilting caused by walnut trees. Phytopathology 11:346. 1921.
6. Davis, Everett. The toxic principle ofJuglans nigraas identified with synthetic juglone, and its toxic effects on tomato and alfalfa plants. Amer. Jour. Bot. 15: 620. 1928.
7. Greene, K.W. The toxic (?) effect of the black walnut: Northern Nut Growers' Assn., Proc. 1929: 152-156. 1930.
8. Jones, L. R. and W. J. Morse The shrubby cinquefoil as a weed. 16th Ann. Rpt, Vt, Agr. Expt. Sta. 188-190. 1902-03.
9. MacDaniels, L. H. and W. C. Muenscher Black walnut toxicity. Northern Nut Growers' Assn., Proc. 1940 172-179. 1941.
10. Massey, A. B. Antagonism of the walnuts (Juglans nigra I.andJ. cinerea.) in certain plant associations. Phytopathology 15: 773-784. 1925.
11. Pirone, P. P. The detrimental effect of walnut to Rhododendrons and other ornamentals. Nursery Disease Notes 11; 1-4. 1938.
12. Plinius Secundus, C. The historie of the world. English translation by P. Holland, A. Islip, London. 1601.
13. Schneiderhan, F. J. The black walnut (Juglans nigra L.) as a cause of death to apple trees. Phytopathology 17: 529-540. 1927.
The toxicity or antagonism of black walnut roots and those of certain other plants has been a controversial question. L. H. MacDaniels and W. C. Muenscher in a report on page 172 of the Thirty-first Annual Meeting of the Nut Growers' Association held in 1940 cited evidence pro and con relative to the toxic effect of black walnut on various crops. They concluded that because of conflicting evidence, the problem of walnut toxicity was still unsolved and needed further investigation. In 1942, Babette I. Brown reported on page 97 of the Thirty-third Annual Report of the Northern Nut Growers' Association, on the injurious influence of bark of black walnut roots on seedlings of tomato and alfalfa. It was concluded, from carefully conducted tests, that walnut roots produce a substance that may be injurious to certain other plants. Experimentation showed that the walnut root bark produces a substance that is injurious to alfalfa and tomato seedlings.
During the past years, a number of instances of stunting and wilting of tomato plants in the vicinity of black walnut trees has been observed. In 1942, a very definite case of wilting and stunting was noted in cabbage plants growing in the vicinity of a black walnut tree.
Severely wilted tomato plants were observed on July 30, 1943, in a field of tomatoes near Egypt, New York. This case was typical of others observed in tomato fields in recent years. The wilting and stunting were all located in one corner of the field, on both sides of which large black walnut trees were growing, and extended out in the field for a distance somewhat greater than the height of the trees. The rest of the field planted with the same stock of tomatoes was entirely healthy. The field had been planted to beans in 1942 and prior to that had been in grass for at least 7 years. The vascular bundles of affected plants were browned as in Verticillium or Fusarium wilt and in some bacterial diseases. No cankers or discolorations were observed on the external parts of the plants. In order to determine whether or not the wilting was caused by a fungus or bacterium, plants were collected for microscopic examination and for culturing to show possible presence of pathogens. The microscopic examinations showed the absence of fungi or bacteria in the vascular system or other plant tissues. The browning in the vascular bundles appeared to be confined to the phloem tissue. All attempts to culture a pathogenic fungus or bacterium from affected tissue was negative. Portions of diseased plants with discolored vascular bundles were placed in a damp chamber and no fungus or bacterial growth developed from the vascular system. From these field and laboratory studies, it was concluded that the wilting and stunting were not produced by a plant pathogen. Since the affected plants in the field were all confined to the area adjacent to black walnut trees, and the fact that it had been shown that the bark of this tree does produce a substance that is toxic to certain plants, it was concluded by circumstantial evidence alone that the wilting possibly was due to black walnut toxicity or antagonism of some sort.
In August of 1942, studies were made on wilted and stunted cabbage plants growing in a semicircle on one side of a field adjacent to a walnut tree (Fig. 1). The field was located near Hall, New York, in a region known to be infested with cabbage yellows. From a distance, the affected plants appeared to have yellows, but upon close study, it was found that they were merely wilted and stunted and did not show the other typical symptoms of the yellows disease. The root systems of wilted plants did not show the presence of club root or black rot infection. The plants in the field were all of one variety and came from the same seed bed. Microscopic studies and attempts to culture a fungus from the vascular bundles of affected plants showed the absence of any fungus that might have caused, the disease. Since the affected plants showed nosymptoms of known cabbage diseases and as they were growing in a semicircle adjacent to a walnut tree, it was concluded that the presence of the root system of this tree might have been the cause of the trouble.