+Walnut and Hickory Plantings+
At the orchard of the Department of Pomology of Cornell University there is a large collection of walnut and hickory varieties and other nut trees. It is not known exactly what the temperatures were in this location but an exposed location half a mile distant had a minimum September temperature recorded of 24°F. and minimum winter temperature of -20°F. The planting in question is on two levels and on a hillside. The damage on the hillside and the upper level was relatively less than on the lowlands where apparently the air drainage was poor. Probably the temperature in the lowlands may have reached 20°F. in September and -25°F. in the winter. At any rate, the damage to the trees was much more severe than in the West Hill location where the temperature reached 23°F. in September.
Injury to the black walnut on the higher land and on the hillside was mostly the killing back of the twigs and smaller branches. On some trees, the petioles of last year's leaves were still attached to the dead twigs late the following summer, showing that the freeze occurred before the abscission layers had formed. The dozen or more varieties of black walnut on the higher land showed little difference between them except that the Elmer Myers showed somewhat greater injury. On the low ground, many varieties including Murphy, Edmunds, Benton, Ohio, Todd, and Stambaugh were killed to the ground or back to the main branches of the trunk. Of three Thomas trees, about 20 years old, one was killed outright, one severely injured, and the other injured only in the twigs. Apparently the difference in these three trees was related to the size of the crop on the trees, although no definite data are available on this point. Walnuts showing little or no injury were: Mintle and Tasterite. Neither of these had had a crop in 1947.
Many of the varieties of hickory were injured as was the native bitternut, Carya cordiformis. This injury consisted mostly of the killing back of the lower limbs and twigs with some varieties being killed outright. Killing of the lower limbs as compared with the tops of the trees is probably related to lower temperatures near the ground due to temperature inversion and possibly to the fact that the lower branches were somewhat weaker in their growth. This sort of injury is common with fruit trees.
On the higher ground the Chinese chestnut trees planted some 20 years ago showed considerable injury. About 50% of them were killed and others were damaged in the lower branches. Chestnut trees in this planting had all survived the cold winter of 1933-34, with winter temperatures below -30°F., so that it is probable that the early freeze of September 27 was responsible for their death.
Japanese walnut seedlings again showed great difference in hardiness, the more tender seedlings killing to the ground and others showing little damage.
Northern pecans on higher ground showed severe damage, the killing extending to the trunk and larger limbs. The variety Burlington, which is a hybrid, pecan x shagbark, showed little injury.
In a planting of several hundred seedling black walnut trees in another location the temperature on September 27 was probably around 18-20°F. About 20% of the trees were killed to the ground. These trees were growing under a sod mulch, were not overly vigorous, and for the most part had not come into fruiting.
In the 1947-48 winter about half of the sweet cherries in the Pomology orchard were killed and peaches were severely injured. No injury was apparent on apple trees.
Weather conditions such as occurred in 1947-48, though unusual, are to be expected occasionally in the latitude of Ithaca, and in fact throughout the northern states. Apparently the fall freeze was widespread as it was almost impossible to obtain any black walnuts that were of any value. Some of the specimens received from other sources obviously had been frozen. The possibility of such damage might well be a deterrent on planting black walnuts in any considerable acreage as a commercial venture in the north. The experience of the past year certainly emphasizes the fact that as yet our knowledge of varieties is incomplete and also that the Northern Nut Growers Association has much work to do in either locating or developing varieties of greater hardiness or with growth characteristics which provide early maturity and thus immunity from early frost damage.