WEATHER IN CRANBERRY CULTURE 21 



summer caused b\- previous injury to the old leaves which reduced their capacity 

 to form carbohydrates. Since the old leaves are known to carry on photosynthesis 

 throughout the summer the\ probabh- supply a large part of the food materials 

 for the growth of the new portion of the uprights. After the new leaves are fully 

 grown the old leaves aid in accumulating stored food. Since the old leaves also 

 niay supply a large part of the food for the growth and ripening of the fruit, up- 

 rights which have lost all or most of their old leaves usually bear no fruit. Vines 

 of all three varieties inside the cylinders lost more of their old leaves than did 

 vines outside; those of the Early Black variety inside the cylinder lost nearly all 

 their old leaves. Even when the old leaves remained on the vines, many of them 

 were injured and accordingly were less effective in the formation of carbohydrates. 



PRESENT STATUS OF THE PROBLEM 



It is evident from the facts presented that some phases of the problem of injury 

 to cranberry vines as a result of a lack of dissolved oxygen in the water during 

 the winter-flooding period are understood much more fully than others. The 

 conditions which determine the dissolved ox>gen content of the water on winter- 

 flooded bogs seem to be quite fully known although some details require further 

 study. On the other hand, very little is known concerning other phases of the 

 problem, specifically, the ox>gen requirement of various parts of the cranberry 

 plant (old leaves, flower buds, and undeveloped new leaves within the terminal 

 bud) under winter-flooding conditions, and the relation of the amount of stored 

 carbohydrates to the ability of the vines to withstand a lack of oxygen. The 

 effect of the size of the preceding crop and of autumn weather conditions, par- 

 ticularly the amount of solar radiation, on the amount of stored carbohydrates 

 in the vines at the beginning of the winter-flooding period should also be known. 

 Knowledge of these relations is especially important because of its bearing on 

 possible remedial or preventive measures. 



SUGGESTIONS FOR PREVENTING WINTER-FLOODING INJURY 



Some modifications of winter-flooding practices may be suggested as remedial 

 or preventive measures. First of all, bogs should be flooded as shallowly and for 

 as short a time as possible. Cranberries are not adapted to being under water; 

 under natural conditions they are usually entirely out of water, or at most only 

 partly covered during the winter. When out of water they depend upon a cover 

 of snow for protection against winterkilling; if partly covered they become frozen 

 into the ice with the advent of freezing weather. 



Bogs in Massachusetts usually need not be flooded before the first week of 

 December and the water should be taken off, if possible, about April L It 

 would be necessary to hold the winter flood later on bogs which have a limited 

 water supply for the protection of the vines against frost during the spring. 

 Late holding of the water may not be particularly harmful; late-held bogs often 

 produce a good crop. Bogs in W^Isconsin usually are flooded about November 

 15-20, and the water is then held until the middle of April or the first of May. 

 However the usual winter-flooding period, both in Massachusetts and In Wiscon- 

 sin, might be shortened when the weather permits. 



The winter flood also should be as shallow as possible; barely enough to cover 

 the vines is all that is needed; It should not be more than 12 to 15 inches. Little 

 or no harm will result even if occasional patches of vines are not completely 

 covered. On the bogs that are out of grade, flooding only to this depth would 

 leave parts of the bogs entirely without water or so shallowly flooded that most of 

 the vines on the higher parts would be above water, but could be done, in many 



