One of the most common types of injury to young nut trees as well as others is that known as "sun scald" or "winter injury". This occurs generally on the south or southwest sides of the trunk and for some distance between the ground and the head of the tree. Usually the injury is not evident until a year or so after it occurred and then it may be observed as a narrow strip of discolored and sunken bark which may crack where it meets the live tissue. This dead or injured area is usually invaded by borers of one or more kinds. This so-called sun scald injury is thought to be caused by the alternate freezing and thawing of the tissues on the south and southwest sides of the tree. On a bright, sunshiny day, even though cold, the sun's rays striking the bark of the tree quickly raise the temperature of the bark and wood. When the sun is obscured by clouds or at nightfall the temperature of the tissues drops rapidly and they may freeze again. It is thought that the rapid and rather great change in temperature of the bark and wood is the primary cause of sun scald. Whatever the cause, we know that it can be prevented by shading the tree trunk. This can be done by heading the trees low so that the branches shade the trunk, or by shading the south side of the trunk with a board 6 or 8 inches wide, or by wrapping the trunk with burlap or similar material. Much of the injury to Chinese chestnut, pecan, and hickory trees, especially, is caused by inexperienced growers who cut off the low branches in an effort to raise the head of young trees. The Chinese chestnut generally forms a very low-headed or bush-type tree. Most of the cold or winter injury I have seen on Chinese chestnut trees has been on the trunks and has resulted from removing the lower limbs so that they were not shaded. Hardiness in woody plants is only a relative term and is determined by the condition of the plant at the time the low temperature occurs. Woody plants are most tender when they are most actively growing and most resistant to cold injury when they are in deep or profound rest. Strong, vigorous, well-nourished trees are much more resistant to cold injury than weak, poorly-nourished trees. Hence, the successful grower makes an effort through disease and insect control and proper fertilization and cultivation to keep his trees strong. These practices should be so carried out that the trees will make a strong, vigorous growth in the spring and early summer and then go into rest without a second or third flush of growth. The trees should carry their leaves until frost as there are some things made in them that cause the trees to develop resistance to cold injury. Winter or cold injury can destroy in a single night the hopes and expectations of several years' work but, in the main, if one grows well only those trees that are suited to the environment such losses are only rarely experienced. Nut Culture In Ontario