By C. A. Reed, U. S. Department of Agriculture

Nut trees of most species commonly thrive at both latitudes and altitudes much greater than the limits of regular or even frequent crop production. This fact is seldom fully appreciated by prospective planters, particularly in the North, who, not unnaturally, assume that the presence of a group of vigorous appearing trees, or even of a single tree, particularly in a fruitful year, is sufficient evidence of local hardiness to justify commercial planting. However, practically all of our native species of nut-bearing trees are indigenous well beyond the range of regular crop production. This is made possible by occasional seasons favorable to seed production which enable such species to reproduce themselves. A crop once in a quarter century would be sufficient for this purpose.

Taking the pecan as an illustration of how a species may be affected by latitude, it has been found that, as the limits of hardiness are approached, the ill effects on the species in approximate order are:

(1) reduction in size of nut, especially with oblong varieties
in length,
(2) increased proportion of faulty kernels,
(3) increased irregularity of crop,
(4) practical crop failure, and lastly the
(5) partial, then complete, destruction of the tree.

On the other hand, the fact that a tree is subject to occasional winter injury, or that it bears irregularly, or not at all in a particular site, is not necessarily to be taken that the same tree in a different site or under slightly changed environment would not perform satisfactorily, even in the same locality. A change in exposure or of cultural treatment, or of rootstock, or of variety, or a modified association of varieties, might and frequently does bring about entirely different results. Sometimes a southern exposure causes trees to respond to mild weather, in winter or early spring, and to be caught by subsequent, violent drops in temperature. Some of the best known and best performing Persian walnut trees in the East are on a northwestern exposure, yet the species is commonly not hardy in the temperate portions of this country.

To a certain extent the ability of orchard trees to withstand frost injury is subject to control. The danger is greatest with trees which have grown late or those which have become devitalized for some reason or with those which are in poorly drained soils. The kind of root stock which has been used, is known to have had an influence in some cases. Doubtless this will be better understood as different stocks are used by the leaders in pecan breeding. Varieties also are known to differ greatly in their degree of hardiness. However, failure upon the part of otherwise normal trees to bear paying crops with regularity is not necessarily due to low temperatures. Other factors, such as self-sterility, may be wholly responsible for at least the lightness of crops.

So far as the orchardist is concerned, a tree is not hardy unless it is capable of bearing crops the average of which are profitable. On the other hand, occasional winter injury does not prove that a species cannot be grown successfully in the same locality. Neither the peach nor the apple industries of the North nor those of the citrus in the South and California nor, in fact, any of the other horticultural commodities of this country are wholly unaffected by frost damage. Our forest trees may be more subject to winter killing than we suspect. A certain amount of winter-injury is to be expected in any part of the country no matter what the species of plant may be.

The frequency with which winter or spring injury is definitely known to occur gives color to a rising theory that freezing temperatures may play a vastly greater part in the development of the nut industry over the entire country than is commonly supposed. Much of the evidence of damage from this cause is of such nature as to be easily overlooked or attributed to other causes. Trees and plants of many kinds have become so accustomed to injury by freezing that they are able to recover without the injury always being apparent. A few illustrations of this which have come to the writer's attention might be cited.

In December 1919, a sudden drop in temperature of from 32°F to 24°F occurred at McMinnville, Oregon, with fatal result to cultivated trees and shrubs of many kinds. The damage was greatest in flat bottoms, especially those where neither land nor air drainage was good. Under such conditions, numerous apple orchards were killed outright. Prunes and Persian walnuts were so badly injured to the snow-line that subsequently great numbers of trees were cut down. Both staminate and pistillate buds of filberts above the snow were practically all destroyed. Later on, the entire tops of many of the older-bearing filbert trees succumbed. An instance of particular interest, in so far as this discussion is concerned, was afforded by the behavior of a shagbark hickory tree in McMinnville, some 20 or 30 years old, which had been grown from a Missouri seed. In February, when examination was made of the condition of this tree, it was found that all visible buds had been killed, yet the bark on the branches between the buds was in apparently perfect condition. The question as to what the tree would do, therefore, became one of great interest. The following September, when revisited, this tree was found to have such a wealth of luxuriant foliage that the observer felt that the accuracy of his February records was challenged. However, closer inspection showed that growth had entirely taken place from adventitious buds, and that the dead buds and spurs were still in evidence. There were no nuts on the tree but otherwise the casual observer would not have suspected that the tree had been affected in any way. In all likelihood, the owner of the tree would deny that it had been injured.

Another case of somewhat similar kind occurred early during the present year in a pecan orchard in South Georgia. The trees had been set in 1917, and in 1919, a portion selected by the Bureau of Plant Industry for conducting a series of fertilizer and cover-crop experiments. The summer of 1923 was extremely dry. This was followed by warm rains in the late fall and early winter. On January 6, during a period of high wind, the mercury dropped to within a few degrees of zero, official reports recording temperatures of from 6 to 8 degrees above zero at various nearby stations.

On March 31, Dr. J. J. Skinner, of the Office of Soil Fertility Investigations, in attending to the spring fertilizer applications, discovered that a high proportion of the trees had been badly winter injured, as indicated by the usual characteristic evidence. These included a considerable exudence of sour and frothy sap from the trunks of the trees, particularly those having smooth bark. This invariably occurred on the west side. Shot-hole borers, which not infrequently follow such injury, were already at work.

This situation was at once called to the attention of the owner of the orchard who lived some 50 miles away. He replied that although he made frequent visits to the orchard, the matter had not attracted his attention, nor had it been reported to him. On April 17, he inspected the orchard and the day following, reported to the Bureau by special delivery that as a result of a rather hasty inspection, he was convinced that from 16 to 20 per cent of the trees in the experimental tract were injured, but that in the rest of this orchard the injury was insignificant, probably not exceeding 4 per cent. His not unnatural deduction was that the high fertilization of the soil in the experimental tract had caused tender growth which, under the extreme conditions of the previous months, had been unable to survive.

On April 24, a careful record of the condition of all trees in this tract and of a representative number of those in adjacent parts of the orchard, was made by Mr. J. L. Pelham of the Bureau of Plant Industry and the writer, in company with the owner of the orchard and his superintendent. It was found that in the experimental tract, 50 per cent of the trees had been visibly injured, thus exceeding the owner's maximum estimate by about 30 per cent. Of the total number of trees, 20 per cent were regarded as being slightly injured, and 30 per cent severely so. Of the fertilized trees within the experimental tract, 55 per cent showed injury to some degree as compared with 58 per cent of the trees unfertilized, also within the tract.

Inspection of the trees outside of the experimental tract showed that 52.6 per cent were affected, 40.8 per cent being slightly, and 11.8 per cent severely injured. A second inspection made June 9 showed that while a few of the most severely injured trees had succumbed, the apparent condition of the majority was greatly improved. In the experimental tract 6 per cent were dead, 13.50 per cent in doubtful condition, and 80.25 per cent were apparently in good condition. Of the trees in outside tracts, the percentage dead, doubtful and apparently sound were 2.80, 9.008 and 87.42, respectively.

The lesson of present importance from this narrative is that afforded by the illustration not only of the ease with which the matter all but escaped the attention of a careful grower but of the difficulty of even impressing upon him the full gravity of the situation. In spite of a prejudice which he conceded was in his mind, when he first inspected the trees on April 17, he underestimated the number affected by from one-third to one-half.

This grower was not alone in his failure to detect evidence of winter injury as was subsequently proven by the negative replies to a general inquiry to growers in many sections sent out in May, together with numerous reports of severe injury received during June and early July. The fact is that winter injury was more or less general in the pecan orchards of much of the South. Had it been possible to observe further, it is highly probable that a direct relation would have been found between this damage and the lightness in the set of the crop of nuts in 1924 over the general pecan district.

Other instances of damages to nut trees which have largely escaped notice might be cited, but these will perhaps be sufficient to call similar cases to the minds of other observers. Of particular interest in the northern part of the country are specific instances of the behavior of individual species and their varieties with reference to ability to withstand local climatic conditions. To cite a few: Mr. E. A. Riehl, of Godfrey, Ill., 8 miles from Alton, reports that during his 60 years of residence on a high bluff overlooking the Mississippi, the pecan trees in the river bottoms of the immediate neighborhood have fruited with exceeding irregularity. A correspondent from Evansville, who cleared 200 acres of forest land along the Ohio of all growth other than pecan, reports that the yields have been disappointing. F. W. McReynolds of Washington, D. C. has 50 or more grafted trees now 8 or 10 years old, 10 miles north of the District, which, although in otherwise thrifty condition, have not fruited.

T. P. Littlepage of Washington, D. C., has some 30 acres of pecan trees, also grafted, on his farm near Bowie, Md., which have borne some nuts during the last three years, but the product has been undersized, poorly-filled and distinctly inferior. Mr. Littlepage reports that during the past spring, these trees suffered appreciable injury in the freezing back of the fruit spurs and that the nuts which formed were from a second set of spurs. His trees bore in the neighborhood of a bushel of nuts which looked more promising than usual until the middle of October when freezing temperature occurring between the 14th and the 24th, completely destroyed the crop. At Bell Station, near Glenndale, Md., about three miles nearer Washington than Bowie, at Marietta, a colonial plantation, there is a clump of pecan trees dating back to the days of Thomas Jefferson. These are apparently hardy except in the matter of yields. Dr. M. B. Waite, of the Bureau of Plant Industry, who has long known these trees, states that they bore heavily in one year, about 1912, but that since that time, they have borne very little.

On the other hand, Mr. Albert Stabler of Washington, has 6 or 8 trees of varieties similar to those in the plantings of Messrs. Littlepage and McReynolds and of about the same age, on a farm not far from that of the latter, one variety of which, Major, in 1923 bore some very fair quality nuts. Although small, they were typical for that variety both in respect to size and high quality. The crop of 1924 was practically a failure, the set being very light. In the test orchard of Mr. J. F. Jones of Lancaster, Pa., young trees of several of the better known varieties are making a good start in the way of beginning to yield and in showing no appreciable signs of winter injury. Most of these trees bore light crops last year, (1923) but are practically barren this year.

South of Waynesboro, Pa., on a farm belonging to Mr. G. H. Lesher, there are 7 seedling pecan trees some 50 years old, which not only show no signs of winter injury outwardly visible, but have the reputation of bearing fairly well on alternate years. The present (1924) being the favorable year, the trees had a good sprinkling of nuts in clusters of as many as 5 each, when seen on July 23. A few miles farther north, in the town of Mont Alto, at an altitude of about 1000 feet, near the location of the State Forestry School of Pennsylvania, another tree said to be 65 years old, and having a girth at breast height of 65 inches, on the residence grounds of Mr. H. B. Verdeer, is apparently as hardy as are the indigenous species of the neighborhood. It is claimed to have recently borne three pecks of nuts in a single season, and it now has a very good crop. Numerous other instances of pecan trees in the North might be cited, but these suffice to establish not only the uncertainty of hardiness of the pecan in the North, but also the probability of nut crops in occasional years or oftener, well beyond the generally accepted range of the species.

The hardiness of the Persian walnut is difficult to define. To again quote Dr. Waite, "Juglans regia, as we know it in the east and north, frequently succeeds over long intervals of time under conditions of climate, soil, elevation, and general environment suitable for the peach. It is perhaps a trifle more subject to injury by radical drops in temperature, but it recuperates with decidedly greater difficulty." Dr. Waite points out that there is a striking similarity between the requirements of local environment of the Persian walnut and the sweet cherry. It develops that this is a familiar comparison in southwestern British Columbia. Both require good drainage of air and soil, or the benefit of moderating influence such as is afforded by large bodies of water. Also both are endangered by warm spells during the dormant months.

These statements cover the situation quite correctly, as it is seen by the writer, although it might be added that beyond or west of the Ohio River, in the middle portion of the country, this species is seldom able to survive for more than one or two winters. Many trees have been planted in Michigan, but the great majority have passed out entirely even where peaches normally succeed. However, it is the experience of a few growers in Sanilac County, bordering Lake Huron, that within a half mile of the lake, there is a greater profit in Persian walnuts than in peaches. One grower at Lockport, New York, has found Persian walnuts to pay better than other orchard crops which he has raised at equal expense or upon equal areas of land. An orchard at East Avon, widely known at one time and visited by the Northern Nut Growers' Association in 1915, practically succumbed entirely after having borne but one good crop in about 35 years. Mr. F. A. Bartlett, of Stamford, Conn., who knows intimately many dozen trees of this species within a radius of 50 miles of New York City, finds that few bear significant crops except at long intervals. From Stamford, Conn., near the Atlantic Seaboard, south to Norfolk, Va., Persian walnut trees are not uncommon in door-yards. They are fairly frequent in southern Pennsylvania west over practically half the length of the State and through Maryland west to Hagerstown. There are perhaps more productive trees in Lancaster County, than in any other county in either Pennsylvania or Maryland, with the possible exception of some county of the Eastern Shore of the latter state, which section already has been referred to. In Lancaster county yields are sufficient to give considerable profit from trees not occupying expensive land.

The Japanese walnut affords a curious analogy in regard to hardiness. During normal years, it succeeds over practically the same range as that of the black walnut, yet it freezes in early fall, mild winter or late spring when conditions are adverse, even when black walnut and pecan nearby are not visibly affected. Mr. Jones finds the Lancaster heartnut, a variety originating in his county, to be subject to injury by spring freezing to such an extent that he has largely discontinued its propagation. Mr. Edwin A. Surprise, of Boston, reports that this variety grows well in summer but freezes back in winter about as much as it grows in summer. Mr. Bartlett regards it as one of the most valuable acquisitions in his nut planting at Stamford, Conn., as it is a handsome, vigorous grower, and promises to bear well. As a safer variety in the Lancaster district Mr. Jones has substituted the Faust from Bamberg, S. C., which vegetates later in spring and thus far has proved less subject to injury.

The twigs of young black walnut trees are occasionally injured by freezing in winter, but recorded instances of such damage are rare. This is a field which should be investigated, as there is evidently no data showing even the regularity with which the black walnut bears in any section, much less the extent to which fruiting is restricted by destruction of the buds or spurs as a result of severe temperatures in winter or spring. This also applies to hardiness of the butternut, the hickories and of introduced species of chestnut.

In conclusion, it is pointed out that planters should not assume that the presence of a healthy tree is proof of sufficient hardiness to warrant extensive plantings, neither should they over-look the fact that an occasional satisfactory crop may be but slim evidence of commercial possibilities. It requires years of trial before a species or variety can fully establish its hardiness. Yet, on the other hand, to wait to find a kind of nut a hundred per cent hardy under all conditions, would be not to plant at all. No varieties of any species are immune to winter injury over any great portion of the United States. The planting of nut trees in the northern part of the country is certain to go forward, but for the present, east of the Rockies, large orchards of nut trees of any species or variety must be regarded as fields promising for experimentation rather than of sound commercial investment.

A common error in the minds of the American people is the assumption that to be a success, a thing must be performed upon a large scale. To develop a nut industry, it is imagined that there must be great orchards of hundreds of acres. It is not realized that a great proportion of the walnuts, almonds, filberts, and chestnuts annually imported from Europe, are from roadside, hillside and door-yard trees which could as well have been grown in this country on what is now idle land in thickly populated agricultural districts. No one need expect to attain great wealth from the products of door-yard or waste land trees but the by-product which could readily be salvaged from nut trees, would likely be very acceptable when interest and taxes or other bills come due.