In the case of walnuts and pecans, especially, but also others than are not sprayed for the control of diseases and insects, it is not uncommon for the trees to become defoliated in late summer and while bearing a crop of nuts. Very often this premature defoliation results in the production of a new crop of leaves and some shoot growth. This is one of the worst conditions one can have in an orchard, for the nuts are certain to be very poorly filled and the trees especially susceptible to cold injury. In such a case as this, the nuts withdraw carbohydrates, proteins and minerals from the leaves and wood of the tree for their development and the production of new leaves and shoots has a like effect. This all results in such a severe removal or using up of the materials involved in the development? of hardiness that such trees are very susceptible to cold injury. Woody plants to be resistant to cold injury must be well nourished. Unbalanced mineral nutrition of trees is a very important factor in determining the amount of injury they may sustain from cold weather. In the various parts of the United States the soils on which fruit and nut trees are grown generally do not supply in adequate amounts some one or more of the essential elements required in their nutrition. This condition results in unbalanced nutrition, in that too much of certain elements is absorbed by the trees and too little of certain other elements. Under severe conditions this causes the leaves to be abnormal in size or in form, for them to be chlorotic or to scorch or burn, or for them to drop prematurely. Such leaves do not function properly, they are not able to carry on photosynthesis at a normal rate and hence do not make sufficient plant foods of the proper kinds to properly nourish the trees. This results in disorders of various kinds said to be due to mineral deficiencies. Among these deficiencies that have been found to reduce tree growth and yield and to increase susceptibility to cold injury are (1) boron, (2) copper, (3) iron, (4) magnesium, (5) manganese, (6) nitrogen, (7) phosphorus, (8) potassium, (9) zinc, and others. In all cases the corrective treatment to be given consists in supplying the trees with the element or elements in which they are deficient. These must be supplied in an available form and by such methods that they can be absorbed by the trees.