6 MASS. EXPERIMENT STATION BULLETIN 433 



reduction occurs in spite of the favorable effect on cranberry size of high tem- 

 peratures in that month.^ The harmful effect of high temperatures in July is 

 probably due to the burning of flowers and small berries which occurs rather 

 commonly on the bogs in hot weather. Storage losses seem to account mainly 

 for the reduction caused by warm weather in September and October. 



The effects of spring temperatures on the cranberry crops of Wisconsin, shown 

 in Table 8 and Figures 6 and 7, are very great. It is impossible, with our present 

 knowledge of these matters, to say just why high temperatures in March'' of the 

 year of the crop are so destructive there. Probably the relation is somehow 

 indirect. The very favorable effect of a warm spring in the year before the crop 

 year suggests that in years with cold springs the growing season in Wisconsin is 

 not long enough for best results. Because of the relatively great variation in the 

 mean temperatures of the spring months in that State, in conjunction with the 

 very steep seasonal rise in temperature in the spring (compare the material at 

 the ends of Tables 11, 13, and 16), warm springs in effect extend the growing 

 season. The temperature means at La Crosse, Wisconsin, show practically the 

 same degree of correlation as those at Meadow Valley. 



Precipitation 



The relations between variations in amounts of precipitation and cranberry 

 production in the three states are shown as follows: Massachusetts, Table 9 

 and Figures 8 to 16, inclusive; New Jersey, Figures 17 to 20, inclusive; Wisconsin, 

 Figures 8 to 12, inclusive. They are summarized briefly here. On the whole, 

 and all three of the cranberry-growing districts considered, it appears that, with 

 the possible exception of frost, excessive rain in the growing season has been the 

 outstanding weather factor limiting production. 



Massachusetts. — The precipitation in the crop year seems to be a major 

 influence in cranberry production. Abundant precipitation in March and April 

 (Table 9) is probably moderately beneficial because it builds up water supplies 

 for use in flooding in the spring frost season. Monthly rainfall of two to four inches 

 throughout the growing season (May, June, July, and August) is evidently con- 

 ducive to large production (Figures 13, 14, and 15). Definite drouth in any month 

 of the growing season is harmful (Figure 13) but appears to be less so than exces- 

 sive rainfall (Figure 15). Drouth seems to be most harmful in August and an 

 excess of rain in July (compare Figures 10 and 11). It should be remembered, 

 however, that plentiful rain in July and August helps the size of the berries 

 (Table 9A) and that the related crop reduction shown in Figures 10 and 11 occurs 

 in spite of this. The indication that excessive precipitation in May and June 

 reduces the crop, without any evidence that it impairs the keeping quality of the 

 berries, strongly suggests that its adverse effect is largely physiological. The 

 material in Table 6 indicates pathological effects of too much rain in July and 

 August. Figure 12 seems to indicate some reduction of the crop from heavy rain- 

 fall in September and this may be pathological. The physiological and patholog- 

 ical effects of drouth and rainfall, in addition to those of other indicated weather 

 i nfluences, seem sufficient to account for the variations in the crop without giving 

 important consideration to the possibilities in flower fertilization. The latter, 

 however, should be investigated much more carefully and extensively than it 

 ever has been. 



^Mass. Agr. Expt. Sta. Bui. 402, 1943, pp. 85-88. 



^The period of this influence seems to include a part of April also. 



