50 



MANUAL OF TREE DISEASES 



Fig. 1.— Frost- 

 cracks in a maploi 

 which have opened 

 for several succes- 

 sive winters. 



Frost-Ceacks 

 Caused by low temperatures 



There are two sorts of 

 frost-cracks which are 

 common types of injury 

 to trees caused by low 

 temperatures. Some 

 frost-cracks may rupture 

 the bark and result in 

 open splits in the trunk 

 (Fig. 1). The calliising 

 at the edges of this split 

 and the repeated opening 

 and healing usually result 

 in a ridge of tissue which 

 increases in prominence 

 year after year (Fig. 2). 

 At other times, frost- 

 cracks which do not rup- 

 ture the bark may occm- 

 in the wood. These 

 either do not show ex- 

 ternally or appear as 

 slight frost-ridges. They 

 are important when the 

 trunk is to be utilized as 

 lumber, since the defects 

 cause the product to be 

 of inferior quality. The 

 splitting open of trunks 

 is more common with 

 some trees than others. 

 Deciduous trees with 



Fig. 2. — The same 

 tree shown in Fig. 1, 

 as it appears during 

 the summer. 



