WEATHER IN CRANBERRY CULTURE 31 



WINTERKILLING 



Cranberry vines sometimes are killed extensively by exposure to winter weather 

 in all the important districts where they are cultivated except those on the Pacific 

 coast. This injury is most widespread when streams, ponds, and reservoirs are 

 low from restricted rainfall and large acreages cannot be flooded till well into the 

 winter. It therefore commonly occurs fairly early in the winter when it reduces 

 the crop total of a state seriously. In Massachusetts it may happen at any time 

 from early December to the end of March. Dry bogs may, of course, be hurt in 

 any winter if there is little or no snow cover and the right weather conditions pre- 

 vail. 



The more common form of cranberry winterkilling seems to be the same as that 

 which sometimes affects fall-sown grains and evergreen trees and shrubs. It has 

 been called physiological drouth}'^ and is caused by the drj'ing out of the vines by 

 transpiration from the leaves while the roots are encased in frozen soil or the 

 stems are frozen so that no water can come up through them. The injury, there- 

 fore, usually occurs in a period of strong dry winds and it generally takes several 

 more-or-less successive days of this to do much harm. This injury always kills 

 the winter fiow^er buds. It may affect only the terminal parts of the upright 

 branches or kill the vines entirely down to the ground. It may kill the more 

 exposed vines and not harm those underneath, where the vining is heavy. It 

 seems never to kill the cranberry roots much in Massachusetts and New Jersey, 

 new growth coming up the following summer to produce at least a partial crop the 

 next year. Vines sticking out of the ice of the winter flood often winterkill back 

 to the ice, their stems being frozen and unable to carry water up to the leaves at a 

 critical time. The leaves of winterkilled vines become reddish or light brown and 

 fall from the stems readily when brushed. Winterkilled vines recover best when 

 they are not disturbed or treated in any way. 



Vines not picked the fall before and new plantings still in hills do not winter- 

 kill easily. Dry bogs should be picked with "snap" machines and should not be 

 raked until early the following spring so that the vines may not be disturbed 

 much in the fall and so made likely to winterkill. 



In Wisconsin, the winter cold often freezes not only the flowage of the cran- 

 berry bogs completely down to the ground but also the soil under it to quite a 

 depth (p. 26). If the winter water is let off early in the spring from a bog deeply 

 frozen in this way, ice may persist in the soil till early June.i^ The occurrence of 

 much dry weather before this melts will kill the vines if water is not put on again. 

 This is called "springkilling" by Wisconsin cranberry men. It is due to physio- 

 logical drouth and so is a form of the winterkilling already discussed. Small bog 

 areas under some conditions of freezing are lifted higher than their dams and 

 cause anxiety lest they fail to settle below flooding level before springkilling 

 occurs. 



A flooded bog which has the water removed in the winter and Is not protected 

 by ice or snow often winterkills easily and badly. The mechanism of this killing 

 has not been determined. 



Flooding bogs for the winter is the best protection from winterkilling. The 

 water should go on as soon as the sand surface remains frozen all day or, at any 

 rate, as soon as it is hard to kick it through with the heel — usually about De- 

 cember 1 in Massachusetts. The water should be held just deep enough to cover 

 the vines; it is often best to let the highest parts stick out when a bog is much out 



l^Smith, J. Warren, Agricultural Meteorology, 1920, p. 209. 



'^Ice sometimes is found in the soil of marshes in Wisconsin as late as July 4. (Cox, H. J., Frost 

 and temperature conditions in the cranberry marshes of Wisconsin, U. S. Weather Bureau Bui. 

 T, 1910, p. 119.) 



