160 



PREPARING FOR WINTER 



cold weather, the foliage is usually weak and sparse the 

 following spring. This condition is shown in Fig. 58. 



(t>) Killing of Leaf and Fruit Buds, Killing of leaf buds 

 is not a very common occurrence in fruit trees, unless the whole 

 twig is killed back. However, fruit buds of such fruits as 

 peaches, cherries, Japanese plums, and apricots are often 

 killed by low temperatures. This injury can be determined by 

 cutting the buds longitudinally. The injured buds will usually 

 have a black center and the damaged flower parts will be 

 easily seen. 



(c) Killing of Blossoiris, Great losses are occasionally in- 

 curred in fruit sections as a result of freezing temperatures at 

 blossoming time. The resistance of the blossoms to cold is 

 generally greater when they are quite small and before the 

 petals open. This resistance decreases as the petals open and 

 continues to decrease until the small fruits form. The blossoms 

 of peaches, plums, cherries, and apricots, which open com- 

 paratively early, especially if a warm spell occurs early in the 

 spring, are among those most often killed. 



{d) Killing of Roots, The roots of fruit trees are usually 

 much more tender than the tissues above ground. As a result, 

 tree roots may be killed when the portions of tree above ground 

 are uninjured. The internal tissues of injured roots turn 

 brown or black. Injury is generally worse in light, sandy soils 

 because such soils are usually drier, fluctuate more widely in 

 temperature, and become colder than the heavier and more 

 moist soils. If the trees are on hilly, wind-swept locations 

 where the snow is likely to be blown away, more root injury 

 usually occurs. 



The use of cover crops or sod is valuable in helping to 

 prevent root injury. 



GENERAL INFORMATION 



I. Necessity of Maturing and Hardening of Wood Tissues 



Growing and immature tissues are injured at much higher tempera- 

 tures than dormant tissue. Most trees which have been caused to grow 



