BETTER FRUIT 



Pioneer Horticultural Journal of the Pacific Northwest 



Entered as second-class matter April 22, 1918, at the Postoffice at Portland, Oregon, under act 



of Congress of March 3, 1879 



Volume XVI 



Portland, Oregon, December, 1921 



Number 6 



Winter Injury to Fruit and Nut Trees 



By D. F. Fisher 



Pathologist Fruit Disease Investigations, U. S. Department of Agriculture 



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I As in every knozvn fruit grooving | 



I section outside the equ-atorial belt, | 



I one of the key 'proble7ns of the Pa- | 



I cific Coast region is that of learn- i 



I ing how best to minimi%e loss from | 



I cold weather. The grozcer who | 



I knows most about minimizing or er | 



I cafing effects of severe weather in \ 



I his orchard has a big lead over the \ 



I grower who trusts his fate to guess- | 



I work. In this article, from a fafer | 



I frefared by Professor Fisher, is fre- | 



I sented a careful discussion of what | 



I haffens to your fruit and nut trees \ 



i in a freeze and why it haffens. The \ 



I facts and deductions have fractical | 



I af plication because obtained from \ 



I study of effects of the cold snaf of | 



I two winters ago in Oregon and | 



I Washington. The article will have | 



I m.ost timely interest for those zvho | 



I were in the fath of last month^s | 



I early snnzc and storm. | 



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LESSONS of importance were gleaned 

 from study of effects of the ex- 

 tremely cold weather in many parts 

 of the Pacific Northwest two winters ago, 

 which may well be impressed on the mind 

 of every fruit grower. When reports of 

 the very general freeze reached the Depart- 

 ment of Agriculture, together with requests 

 for advice as to methods of procedure in 

 handling the injured trees, the writer was 

 assigned to make a survey of the situation 

 and render possible assistance. 



The office of fruit disease investigations 

 in the Bureau of Plant Industry at Wash- 

 ington has a most complete file of informa- 

 tion on frost damage, collected by Dr. M. 

 B. Waite and his staff over a period of 

 more than 30 years, during which the 

 subject was studied in all parts of the 

 country. The writer, in approaching this 

 Northwestern situation was fortunate in 

 having so much accessible data from other 

 sections to draw on in an analysis of local 

 conditions and upon which to base his 

 recommendations. 



It would probably be well at this point 

 to sketch briefly the different types of 

 injury produced by cold and the factors 

 that influence such injury in general. 



There are several types of frost injury 

 which we may list as follows: 



1. Killing of the fruit-buds, either bv 

 extreme winter cold or by frost during the 

 blossoming period. 



2. Killing of the twig tips usually as a 

 result of winter cold. 



3. Browning or blackening of the wood 

 in the branches or body of the tree, pro- 

 duced by winter cold. 



4. Bursting of the bark from the trunk 

 of the tree, with or without discoloration of 

 the wood. 



5. Lifting of the bark on the south and 

 southwest side of the trunk or branches, 

 this being the condition we know as winter 

 sun-scald. This and the preceding condi- 

 tion is frequently caused by the reflection 

 of the sun's r.ays off the snow, the conse- 

 quent warming of restricted areas of the 

 bark and thereby inducing growth activities 

 within the cells, which render such parts 

 most susceptible to the cold of ensuing 

 nights. 



6. Girdling, or partial girdling of the 

 trees at the ground line, or just below the 

 ground line, resulting in one of the condi- 

 tions know as "collar rot." This is brought 

 about when the snowfall is insufficient to 

 insulate the tender areas at the crown or 

 collar of the tree. 



7. Winter-killing of the roots of the 

 tree, with or without injury from the 

 ground line upward. This likewise results 

 from extreme cold and insufficient insula- 

 tion of the roots by snow or otherwise. 



I 



T IS NEVER easy to determine the 

 degree of severity of any type of frost 

 injury, as no doubt some of you can testify 

 from your experience. The severity of 

 injury usually varies from tree to tree and 

 in different parts of the orchard. 



The various types of winter injury are 

 the result not alone of the degree of cold, 

 but of a combination of the weather con- 

 ditions and the condition of the trees, and 

 in most cases the latter factor is the more 

 important. The conditions of the tree 

 which influence its susceptibility to frost 

 damage may be outlined, in the order of 

 their importance, as follows: 



1 . The degree of dormancy of the 

 principal parts involved. (A completely 

 dormant tree is far more resistant to cold 



than one in partially succulent condition.) 



2. The species or kind of tree. (For 

 instance, an orange tree is more tender than 

 a walnut, and a peach tree more easily 

 injured than an apple). 



3. The variety. (The so-called Russian 

 varieties of apples like the Red Astrachan 

 and Yellow Transparent are very resistant 

 to cold and survive where others fail). 



4. The age of the tree. (Under some 

 conditions young trees are more resistant 

 than older ones). 



5. Cultural conditions which affect the 

 vigor of the trees, under which we may 

 include the following: 



a. Character of the soil and subsoil, 

 especially its moisture holding capacity, 

 which ties this up with (b) : 



b. Moisture and drainage conditions: 



Twenty-fiveycaroia Italian prune tree 

 ruined by frost damage of 1889 and result- 

 ant heart rot, but still living. 



