522 
Journal of Agricultural Research 
Vol. XI, No. 10 
curves of monthly rainfall 1 (fig. i) indicate, however, that the precipita¬ 
tion of the four eastern localities is similar during the growing season, 
with the exception of the heavier August rainfall in New Jersey, while 
that of North Head, Wash., belongs to a quite different type. 
* LENGTH OF FROSTLESS SEASON 
For most green plants the temperatures of greatest importance are 
those occurring between the last killing frost in spring and the first killing 
frost in autumn. For the cranberry under cultivation the length of the 
frostless season is to some extent artificially regulated, sometimes by 
holding the water late in the spring, often by flooding to avoid early 
frosts in autumn. 
Fig. i.—Curves of the monthly rainfall during 1916 at Middleboro, Mass., Farmington, Me., 
Indian Mills, N. J., North Head, Wash., and Grand Rapids, Wis. 
The average length of frostless season probably furnishes, however, the 
best available indicator of the length of growing season for the cranberry 
and is used as a basis of calculation in the present study. As given by 
Day U)> the average length of the frostless season for these areas is as 
follows: 
Table I .—Length offrostless season in cranberry regions 
Locality. 
Average 
date of 
last killing 
frost in 
spring. 
Average 
date of 
first killing 
frost in 
autumn. 
Average 
length of 
crop grow¬ 
ing season. 
Grand Rapids, Wis. 
May 20 
May 20 
Apr. 20 
Apr. 20 
Feb. 9 
Sept. 20 
Sept. 20 
Oct. 20 
Oct. 20 
Dec. 22 
Days, 
123 
123 
183 
183 
314 
Farmington, Me. 
Middleboro, Mass. 
Indian Mills, N. J. 
North Head, Wash. 
1 The data on the monthly normal rainfall and temperature and the length of frostless season were kindly 
supplied by Mr, P. C. Day, Chief of the Climatological Division of the Weather Bureau. 
