22 MASS. EXPERIMENT STATION BULLETIN 371 



buds. This flood should go on in the night and also be taken ofif at night 

 if tlie weather is very warm, for if tender growing vines stand in water 

 long, exposed to a hot sun, they may scald. The flower buds are less 

 likely to be hurt by the flooding if the weather is clear while the water 

 is on, for light is necessary to the photosynthesis by which the plants give 

 oxygen to the water. Cloudiness with a high water temperature is especially 

 dangerous, for the warmer it is the faster the plants respire and the 

 greater their need of oxygen. The complete flood should not be held on 

 a bog over thirty hours unless the weather is definitely clear and cool 

 and should not be held over twenty hours if the bog has a bad record of 

 injury by June flooding. 



A partial flood must be put on if frost threatens in May or June. Two 

 or three inches of water under the vines is enough, for heat will pass from 

 the water to the air and keep the vines from freezing. If water must be 

 saved and it remains cold, the water may be held over on the bog from 

 one night to another for several successive days up to about May 12 and 

 for a day at a time occasionally after that. 



Cranberry winter buds are not hurt by a temperature of 25° F. till they 

 swell to a diameter of more than 2 mm. They usually will endure tem- 

 peratures down to 20° till the end of April. Temperatures above 29° seem 

 never to do much liarm. Often 28° is reached in the time of tenderest 

 growth without injury, l)ut the greatest depression in such cases is brief. 



Flooding should not he done during or after the l)looniing period, for 

 it will blast the blossoms antl promote rapid development of the fungi 

 that rot the fruit. 



P'rost in September antl Octol)er often necessitates flowing again, but 

 the berries and vines will endure more frost then, and longer chances may 

 be taken than in the spring. The water may be held over on the bog 

 from one night to another occasionally, as in the spring, if it seems neces- 

 sary. Cranberries usually will stand 27° F. in the wiiitish stage before 

 ripening, but 25° harms such fruit greatly. Freezing begins among ripe 

 Early Black and Howes berries at or slightly above 22°, no softening fol- 

 lowing exposure to 23°. Ripe Howes and McFarlin berries are so re- 

 sistant that under bog conditions often only 10 percent are injured at 16° 

 and only 20 percent at 14°. Sometimes, however, 25 percent are softened 

 by 18°. The loss of Early Black berries at these temperatures is much 

 greater. 



Frost flooding always does some harm: in the spring tending to reduce 

 production, and in the fall tending to impair the keeping quality of the 

 fruit and interfering with harvesting. For this reason and because un- 

 necessary frost flooding wastes limited water supplies, accurate forecasts 

 of frosts are very important. Tlie Weather lUireau sends out special 

 warnings to tlu' craiiben y growers, which are supplemented by those of 

 the Cranberry Station of the Massachusetts Agricultural Experiment 

 .Station. 



As soon as the crop is gathered, the bog should be flooded for a week 

 to water the disturbed roots and float oil fallen leaves, berries, and otiier 

 trash.'' This contrf)ls tlie cranberry girdler when it is done late in Sep- 

 tember. No flooding is necessary after this till the water goes on for the 



" If much of this mill ("rial lodRos on tlie 

 catch basins around tlic bop margin to receive 

 been niaiie, the trash iniisl be rakeil from the 



