The Results
Getting survival and performance data on these widely scattered experimental plantings presented quite a problem. Examination of a few plantings showed that trees given reasonable care had survived and were beginning to bear nuts. So in 1946, the farmers who had planted the trees were polled by mail for an overall evaluation of the plantings. Questionnaires asking for information on survival, growth, and bearing were sent by the state extension foresters to 3,274 farmers. The return of questionnaires was excellent. Forty-two percent came back and three-fourths of them were filled out completely.
Survival and Mortality Causes. Eighty-one percent of the 1,373 plantings reported on were still active in 1946; that is, they still had at least one living tree. Survival reports received on 3,831 trees planted showed that 2,439 or 64 percent of the trees were living in 1946. Survival was best in the portion of the Valley north and east of Chattanooga; 84 percent in Virginia, 71 percent in North Carolina, and 66 percent in eastern Tennessee. South and west of Chattanooga survival percent was lower: 62 in Georgia, 61 in western Tennessee, 54 in Kentucky, 45 in Alabama, and 26 in Mississippi (Table 1).
Causes of mortality, as reported, were classified in five categories; losses prior to establishment, livestock and destruction, drought, insects and disease, and unknown (Table 1). Cause of mortality was listed as unknown for 42 percent of all trees reported dead. Field experience leads us to believe that most of the trees in this category probably succumbed to improper planting or complete neglect following planting. Many persons do not follow planting instructions; they often substitute their own methods with disastrous results.
Among the reported known causes, drought killed most of the trees—29 percent. We know black walnut is very susceptible to dry weather after transplanting. Weather records for the area show that the early growing season of 1941 was exceptionally dry; 1942 was also drier that average; in 1943 and 1944 near drought and drought conditions prevailed throughout most of the Tennessee Valley. Weather is usually blamed when a tree dies without apparent cause, but in this case the reported mortality due to drought appears reasonable.
Livestock, mowing, fire, and intentional removal were reported to have caused 13 percent of total mortality. Cows are curious animals and newly set trees seem to arouse all the curiosity in their make-up. Horses and cows apparently do not relish the foliage of walnut trees but they do bite at it, and in so doing usually break down the branches to such an extent that the tree dies. Some trees were accidentally destroyed simply because they had been forgotten. The next highest mortality cause reported was pre-establishment loss; this was blamed for 9 percent of the deaths. Losses resulting from delayed planting were placed in this category, also those where the report was "trees failed to leaf out." Insects and diseases were reported as causing 7 percent of the mortality.
Growth and Bearing. Those who plant improved black walnut trees naturally want to know how soon they will begin bearing. This survey shows that bearing begins much earlier than most people thought. Trees in 32 percent of the plantings established between 1939 and 1944 were bearing by 1946. Of these 342, 113 began bearing 2 to 4 years after planting; 120 bore their first crop after 5 years; 109 began bearing after 6 to 8 years (Table 2). According to the reports, the earlier plantings were slower to come into bearing than the later plantings. This probably is not a true picture. We suspect that after six or eight years the actual date of first bearing had been forgotten in many cases.
Growth was reported in terms of total height for each tree. These heights were then converted to annual growth rates for trees 3 to 8 years old and placed in arbitrary classes are follows: low (less than 1 foot) medium (1 to 2 feet), and high (over 2 feet). Test plantings in North Carolina had the highest growth rate; those in Mississippi, the lowest. In other states, growth rates fell between these two and were quite similar for the most part (Table 3). Average for all trees was 1.6 feet per year. Trees averaging less than one foot of height growth per year were slow to come into bearing. Only 14 percent of the trees in the low growth rate class were bearing. On the other hand, 71 percent of the trees with a high growth rate had come into bearing. Growth of black walnut, following recovery from transplanting shock, depends on site conditions and tree care. Trees set in fertile soil with an adequate moisture supply and kept free of livestock and other damage make rapid growth. Trees set in poor, thin or droughty soil do not make much growth if they survive at all. Black walnut is very sensitive to any wounds and, if subject to mechanical or livestock damage, growth is retarded.
Cases of exceptional growth and bearing were reported. One in eastern Tennessee is worthy of brief description. There were two trees in this planting set approximately 40 feet apart. One was on the edge of a garden; the other, in a chicken run. In seven years the first tree grew to a height of 32 feet—an average growth of 4.5 feet a year. It began bearing in 1943 and produced a crop of nuts each year up to the time of the survey. The 1946 crop, reported as a light one, yielded 3.5 pounds of kernels. The other tree, shown in Figure 1, was 18 feet tall, having averaged 2.5 feet a year. It also began bearing annual crops in 1943, and in 1946 it had a very heavy crop for its size, yielding 2.5 pounds of kernels. Here are two Thomas trees of the same age planted practically side by side; one is almost twice the size of the other, but they both began bearing annual crops three years after planting.
Field Survey in Sample Area. To check on the adequacy of the questionnaire survey, 108 test plantings in eastern Tennessee were visited and inspected. Forty of these had been reported on by mail; 68 had not. In general, the trees had been planted on the best sites available. Some were set out in farm orchards (Figure 2); a large number were planted in yards as combination nut and shade trees (Figure 3).
Field examination of the 40 plantings which had returned questionnaires revealed conditions very similar to those reported (Table 4). Survival was found to be 75 percent compared with a reported 77 percent. Average tree height was reported as 9 feet; actual height averaged 11 feet. There was some hesitancy in reporting tree deaths caused by livestock; 4 percent was reported while 23 percent was found. Such mortality was usually listed as unknown on questionnaires.
Information collected by field examination of 68 plantings which had not returned questionnaires and the 40 plantings which had returned questionnaires is shown in Table 4. Trees were found to be 2 feet taller in the 68 plantings but these trees averaged one year older than trees in the 40 plantings. Trees in the 68 plantings averaged 13 feet in height compared with 11 feet. Average age at first bearing was very similar. And here is a revealing discovery; livestock, mowing, and fire were responsible for 47 percent of the tree mortality in the 68-planting group, compared with 23 percent in the 40 plantings. This is perhaps one reason why the persons involved in these 68 plantings did not return questionnaires; it also explains most of the poorer survival. A large number of trees were planted in pastures and elsewhere without adequate protection from livestock. Even when cattle guards were used they were generally too small or weak for tree protection. Severe livestock damage resulting in poor growth and eventual death of trees was encountered frequently. We are inclined to believe that livestock accounted for a much higher percent of tree mortality than that reported in this survey.
The high percent return of questionnaires in this survey, followed by a field check in a sample area, provides a good picture of Valley-wide plantings. Since survival was found to be lower in plantings which did not return questionnaires, an actual overall survival of 64 percent may be slightly high. Other spot checks in the field will give more information on this point.