The Canadian Horticulturi^ 



Floral Edition 



Vol. XXX VI [I 



AUGUST, 1915 



No. 8 



Winter Injuries in 1915 



W. A. McCubbin, M.A., Field Secretary, Entomological Division, St. Catharines, Ont. 



SU many cases of damage due to 

 winter conditions have come un- 

 der my observation during the 

 past two seasons that a few words on 

 the subject may be of interest. The 

 term winter injury may be used to in- 

 clude those injuries due to winter sus- 

 tained by plants which are either dor- 

 mant, are about to become so, or which 

 are emerging from the dormant condi- 

 tion. It should be noted that while 



'extreme cold may at times cause dam- 

 age it is where the low temperature 

 is associated with other factors that 

 the greatest injuries occur. Among 

 these contributing factors there are 

 several important ones from the point 

 of view of the general grower. Varia- 

 tions in temperature, especially if sud- 

 den and extreme, are to be considered. 

 A tree which would be uninjured by a 

 week's zero weather if during the pre- 

 ceding and succeeding weeks the tem- 

 perature gradually fell to and rose 

 from the low level, would be badly 

 hurt by a very cold week suddenly fol- 

 lowing a warm spell or a warm period 

 abruptly ensuing after a very cold 

 period. 



There is also the protection of the 

 tree to be considered. In the natural 

 state a tree would have a humus-filled 

 soil, an old sod, or a matting of weeds 

 and old leaves around it which would 

 modify very materially the effects of 

 frost. In cultivated orchards where 



■ the bare soil is left freezing takes 

 place more suddenly and extends more 

 deeply, while thawing is more rapid 

 in the spring. This is especially true 

 of hard and earthy soils which lack 

 humus, and in such cases freezing of 

 the roots may be expected. 



The most important factor, however, 

 is the dryness of the plant tissues. 

 When a tree prepares itself for winter 

 growth ceases and the tissues undergo 

 certain changes, associated with which 

 is the drying out of the surplus water. 

 Every effort is made to keep as little 

 water as possible. Here again our 

 methods of cultivation sometimes in- 

 '•rfere Math nature's processes and our 

 wees are hindered from getting rid of 

 water, when, of course, they are not 

 fit to meet the cold of winter, and are 



frozen. We commonly speak of this 

 as "ripening" of the wood in the fall, 

 and while the presence of too much 

 water is the main factor which prevents 

 proper ripening, there are others which 

 also hinder the process to some extent. 

 Among these may be mentioned severe 

 summer pruning, which stimulates a 

 late growth and leaves unripened wood 

 to face the winter. Similarly defolia- 

 tion by insects or fungi may start the 

 tree to putting out new leaves and 

 shoots which are liable to be immature 

 when winter comes on. Also young, 

 newly-set trees which do not have an 

 early start in spring may not get a 

 proper chance to ripen up in the fall. 

 In many trees which are unhealthy the 

 growth processes are slow and an early 

 cold wave may damage them before 

 their wood has had time to become 

 mature. 



In a climate like ours, where there 

 are such variations and sudden 

 changes, we can scarcely hope to en- 

 tirelj' banish winter injuries. We can, 

 however, help our trees to pass the win- 

 ters with more security than has been 

 customary in the past by paying- some 



attention to the factors concerned ui 

 the problem. One might sum up the 

 general methods that may be followed 

 to assist nature in bringing the orchard 

 safely over the winter, as follows : — 



1. Plant trees known to be hardy for 

 the localit}'. ' 



2. Keep the orchard vigorous and 

 healthy. 



3. Avoid late growth of the orchard.. 

 Give it every chance to ripen the wood 

 in the fall. Especially see that it haa 

 not too much water in fall. 



4. Protection measures may be use- 

 ful. A humus-filled soil is good insur- 

 ance against collar rot. A mulch of 

 straw or stra\\'y manure or even a heap 

 of earth will in some cases modify the 

 sudden changes to which an earthy 

 soil is liable. 



Dieback of Shoots: This is a very 

 common form of winter injury. It may 

 be seen in almost any orchard. The 

 shoots are killed back from the end.-J 

 for varjang distances. It is extremely 

 frequent among tender trees like the 

 peach, and among trees not quite 

 hardy for the locality, as for instance, 



>4 '',-%'*> \jjj * 





'*'M\.. 



Indian women picking groo.seberrles. which have been grown as fillers between the fruit trees, 

 in the orchard of Mr. Bell, of Burlington. Ont. 



