22 MASS. EXPERIMENT STATION BULLETIN 402 



cases, without exposing the vines on a very large proportion of the bog to possible 

 winterkilling. Even where a bog is badly out of grade it would be better, prob- 

 ably, to leave the highest parts unpiotected in order to reduce the depth of the 

 water on the lower parts. Winterkilling might cause some reduction in the size 

 of the crop from the higher parts of a bog as a result of this practice, but usually 

 this would be more than offset by the increase in the crop on the lower parts of 

 the bog. 



Injury to the vines from a lack of oxygen during the winter-flooding period 

 may be prevented by two other practices: (1) by freezing the vines into the ice, 

 and (2) bj^ flooding the bog as usual, and after several inches of ice have formed 

 over the bog, drawing the water out from under the ice thus allowing it to drop 

 down onto the vines and remain there until it melts. Both of these methods have 

 been used successfully in Wisconsin, the former more extensively than the latter. 



The first method is not so well suited for Massachusetts as for Wisconsin con- 

 ditions because the temperature, when the bogs are being flooded for the winter, 

 usually is not as low in Massachusetts as in Wisconsin. The same result would 

 be obtained in Massachusetts, however, by flooding bogs very shallowly so that 

 the vines would be frozen into the ice if the weather should become cold enough to 

 freeze ice several inches thick. This happens regularly on nearly all bogs in 

 Massachusetts, but to a much greater extent on some than on others depending 

 on the evenness of the bog and on the depth to which it is flooded. 



The practice of drawing the water out from under the ice has proved very 

 successful on those bogs in Wisconsin on which it has been used and, probably, 

 would be equally successful in Massachusetts. It is a very satisfactory, if not 

 ideal method of bog protection in that the vines are fully protected against 

 winterkilling and at the same time have an abundant supply of oxygen. 



The only factor that might be considered at all unfavorable for vines on bogs 

 on which the water is drawn out from under the ice is that of light. A consider- 

 able proportion of the incident light might be cut off by the ice, the more the 

 thicker the ice; and if the ice is covered by snow, all the light or most of it might, 

 be cut off. This, probably, would have very little adverse effect, however, since 

 the vines would have an abundant supply of oxygen, and normally also an ade- 

 quate amount of stored carbohydrates that could be used to supply the small 

 amount of energy required for their metabolic processes at the low temperatures 

 under which they would be. The temperature of cranberry vines under a layer 

 of ice several inches thick generally is much lower than that of vines in water 

 under ice. Consequently, the amount of stored carbohydrates used in respira- 

 tion, even over a period of two to four months, would be very small, perhaps 

 negligible. Moreover, with an abundant supply of oxygen available, no toxic 

 products would be formed as they are when the oxygen for respiration is obtained 

 by breaking down stored carbohydrates, which is done when the vines are in 

 water containing little or no dissolved oxygen. 



The objections usually expressed by growers in Massachusetts to drawing the 

 water out from under the ice are: (1) That the ice is likely to melt during January, 

 or February, leaving the vines unprotected; (2) the vines would be liable to be 

 pulled out by the lifting of the remaining ice if it were necessary to reflow the bog 

 or if a bog were flooded by a heavy rainfall; and (3) an insufficient water supply 

 might make it impossible to reflow a bog if the winter flood were drawn off. 



It is true that the ice sometimes melts during a warm period which may come 

 at any time during the winter. It is not unusual in Massachusetts for the ice 

 to melt in January, and this happens very commonly in February. In Wisconsin, 

 the ice rarely goes off the marshes in January, it does sonietimes in Februarj-, but 

 usually not until March. 



If the ice melts enough to expose the vines over a considerable part of a bog, 



