140 MASS. EXPERIMENT STATION BULLETIN 192. 



and so an unusually large percentage of the bogs was exposed to the 

 winter. Winterkilling of the vines was as severe and widespread as in the 

 previous winter, and the attending weather conditions were much the 

 same. 



A hard frost occurred the night of June 20, 1918, reducing the pro- 

 spective crop, as estimated, over half. The lowest temperature recorded 

 at the station was 26f° F., and 23° F. was reported from some bogs. The 

 vines had begun to bloom, and many growers used water more sparinglj- 

 than they should have on that account. A widespread effect of this 

 frost was noted later in the season. The vines had failed to recover and 

 form buds for the next year on considerable areas. On such areas, there- 

 fore, the frost really destroyed two crops. 



Frost Studies. 



As the records made at the station during the past five years seemed a 

 fair basis for a study of frost conditions on cranberry bogs on Cape Cod, 

 and as the great loss from frost in September, 1917, made the need of 

 closer predictions seem imperative, the WTiter gave most of the following 

 winter to a careful investigation in this connection. The most important 

 result was a new method for computing minimum temperatures on any 

 night in which frost conditions prevail. The method is probably as 

 reliable for computing on wind}' nights, if they are clear, as on still ones, 

 but much cloudiness during the night renders it inaccurate. 



Predictions bj' the new method are made from readings at 8 p.m., 

 standard time. As a few minutes are needed to take the readings and 

 make the calculation, the forecast is not ready until 8.15. As damaging 

 frost may occur as early as 11 p.m., this warning will sometimes give only 

 three hours in which to flood. Frost flooding can be done on many bogs 

 in this time, but it takes several hours more on most of the larger areas 

 with their present flumes and canals. Many gi-owers would profit by 

 gi-eatly enlarging these equipments so as to flood more quickly and make 

 full use of the warnings obtained by the new method. 



The 8 P.M. temperature at a height of from 17 to 20 feet above the bog 

 level is one of the factors used in the new method. Quite accurate pre- 

 dictions have l^een made for the Atwood bog at South Carver by substi- 

 tuting the shelter temperature at that bog for the station shelter tempera- 

 ture in the formula used in calculating. This suggests that growers may 

 help both themselves and the work by placing Green thermometers in 

 elevated locations near their bogs, and telephoning to the station their 

 8 P.M. reading. 



Blueberry Work. 



On May 14, 1917, thirty-nine swamp blueberry bushes, selected for the 

 quantity and quaUty of fruit they bore in 1916, were transplanted from 

 the wild to the station blueberry plantation at East Wareham. The 

 writer spent a week in New Jersey in late July and early August, 1917, 



