STATE HORTICULTURAL SOCIETY. 217 



inner bark on the southwest sides of nearly all the trees more or 

 less injured. By the middle of May the bark was dead on the 

 southwest sides of my Wealthy apple trees in the orchard. I have 

 noticed similar spells of weather at other times, after the sap of the 

 trees had become liquid and before their buds had opened into leaf. 

 In fact it is not unusual in northern Iowa and Minnesota to have 

 only a few hours of spring weather between winter and summer. 

 In sections of the country where fruit trees have proved most 

 healthy, the change from winter to summer is more gradual. That 

 trees must necessarily be severely injured at such times by such 

 sudden changes of temperature, is very evident to persons who are 

 well informed in regard to the principles of plant growth. When 

 the buds begin to open into leaf, the starch, sugar and other re- 

 serve food materials which have been stored in the cells of trees 

 during winter, are in a liquid condition — in fact the trees are full 

 of thin, watery sap. As there are are no leaves on the trees at 

 such times, there can be no upward flow of sap. And being sta- 

 tionary when the temperature of the atmosphere ranges be- 

 tween 75® and 85^, it will be many degrees hotter than the sap of 

 healthy trees during the hottest days of summer. At such times 

 chemical changes take place which were not intended by nature. 

 The tender inner bark will be not only scalded but poisoned, and 

 the result will be dead bark, and afterwards dead wood. While 

 considering this question, we should not forget that during growth 

 the sap of trees is " pumped up " from the ground by their leaves, 

 and that if they should be removed it would become stationary im- 

 mediately. As evidence of the fact that the upward flow «tf sap 

 is rapid and that its temperature is low (as most of it comes from 

 the cold subsoil), I will remark that it has been proved by many 

 experiments made by skillful scientists, that the upward pressure 

 of sap in healthy fruit trees and grapevines is from five to seven 

 times greater than the pressure of the blood in the arteries of dogs. 

 To protect the bodies of trees from being scalded in the spring, I 

 cannot recommend anything better than protection by boards or 

 paper, or by winding hay or staw bands around them. As I do not 

 wish to become wearisome, I will only add to what I have said, 

 that healthy trees of such varieties as Duchess of Oldenburg, 

 Wealthy and Plumb's cider were never seriously injured by cold in 

 Minnesota, and that apples will be plentiful and cheap in all parts 

 of the northwestern states, when we shall have learned how to get 

 our fruit trees into winter in good condition, and how to get them 

 safely out of it. 



