SEVENTEENTH ANNUAL MEETING. 55 



The probable reason for the greater hardiness of firm 

 and mature growths is that the sap is denser. Dense hquids 

 require a lower temperature to freeze than those less 

 dense. Firm and well ripened woods also have smaller and 

 stronger cells, less easily injured by the freezing and thaw- 

 ing process. 



XIV. 

 Are Young or Old Trees Hardiest? 



Beyond all question young trees suffer most in severe 

 winter freezes. Practically all of my correspondents in both 

 New York and Michigan agree to this, and as a proof many of 

 the Michigan growers give their experience in the several 

 severe freezes that have occurred in that State during the 

 past few years, in which young trees universally suffered the 

 most. It is probable that young trees are injured most be- 

 cause they make a much greater and much ranker growth 

 than the older ones and hence more sap remains in them 

 during the winter. The formation of buds in the older trees 

 is helpful, too, in maturing the wood. There are, however, 

 many exceptions to the statement that young trees are less 

 hardy to cold than old ones. Old trees can be forced to pro- 

 duce large quantities of new wood, susceptible to winter-kill- 

 ing, while on the other hand the superabundant growth of 

 young trees can be kept down by orchard treatment. It is 

 fair to assume, too, that old trees possessing very low vitality 

 are less hardy than vigorous young trees. Thus it was often 

 noted that old trees which had suffered from the ravages of 

 borers or fungus parasites, as curl-leaf or shot-hole fungus, 

 Avere easily killed by cold. 



While young- trees are more susceptible to freezing than 

 old ones, yet they are much more likely to recover, if re- 

 covery is possible, and their return to the normal condition 

 is, more rapid. This is probably true because of the greater 

 vigor of the younger plants and because of the possibility of 

 an entirely new covering of bark for small trees, often impos- 

 sible with larger ones. 



