CLIMATE AND TREE GROWTH 109 



the damage is repeated yeav after year, may lead to poor, 

 stunted, and worthless trees. But such damage is 

 dependent largely upon species and situation, and bad as 

 they are, it is difficult to prove that spring frosts alone 

 are responsible for the failure of the majority of trees to 

 srrow into good timber. 



One serious effect of May frosts is often seen upon 

 newly planted trees which have pushed out a few leaves 

 and then been cut back. In such cases the vitality of 

 the trees is often reduced to such a low ebb that death 

 ensues, and this is especially likely to occur with larch, 

 which is apt to open all its buds at one time, leaving few 

 or none in a dormant state. 



The weather of June usually shows a decided increase 

 in temperature, and if sufficient rain falls, the bad effects 

 of May are quickly obliterated. The old saw that ' a 

 dripping June puts all in tune ' is usually verified, for 

 temperature is seldom low enough to check the growth 

 of plants, provided sufficient rain, or at least two to four 

 inches, falls. But with a dry June following a dry and 

 cold May things get worse instead of better in many 

 respects. Caterpillars, aphides, and leaf-eating insects 

 of all kinds injure or reduce the already stunted foliage, 

 and in place of a healthy, dense, and vigorous leaf canopy, 

 thin crowns of perforated and clammy leaves, infested 

 with various pests, are invariably typical of a dry May 

 and June. 



Although the actual presence of insect pests is not 

 altogether due to the weather conditions at the time, 

 there is little doubt that their increase, and the bad effects 

 they produce, are aggravated by drought and heat, and 

 with stunted foliage the leaf surface presented to them is 

 much smaller than in a growing year, in which possibly 

 the same number may be present, but spread over a 

 larger area, and therefore less conspicuous and injurious. 



