60 THE DATE PALM. 



than on the tops of old palms far above the surface. Old and vigor- 

 ous trees might perhaps occasionally weather cold snaps where the 

 temperature fell below 10 F., provided such were exceptional and 

 occurred only at intervals of many 3^ears. In practice, then, four dif- 

 ferent limits below which palms would be injured by cold might be 

 set: (1) Young palms in active growth would be liable to injury if the 

 temperature fell several degrees below freezing; (2) 3 7 oung plants not 

 in active growth and old palms if nearly dormant would be severely 

 injured only by temperatures falling below 15 F. ; (3) old and dor- 

 mant trees would be severely injured only by temperatures below 12 F. ; 

 (4) most date palms would be killed and all would be seriously injured 

 by the temperature falling below 10 F. , and date culture would be 

 impossible in regions where such temperatures occurred more than once 

 in a decade. These considerations show that the date palm has about as 

 much resistance to cold as the fig tree, for example, with this impor- 

 tant difference that a fig tree is able to recover and grow again the next 

 year, even if it be frozen to the ground by severe cold in winter. 

 With the date palm this is not possible, since, if the growing bud of an 

 old tree be killed, it is impossible for the trunk to sprout out again. 



In the Salt River -Valley, Arizona, the temperature not infrequently 

 falls to 25 or 22 F., and at rare intervals goes as low as 12 or 13 

 F., which temperatures of course injure the date palm but have not 

 killed any of the many fine trees growing in the valley, though young 

 offshoots recently transplanted have been frozen to death a . 



No temperatures low enough to injure seriously even young date 

 palms (below 18 F.) are recorded from any of the stations in the Sal- 

 ton Basing and if the first winter after the plants are set out is passed 

 safely no further danger from cold need be feared. 



a Even young palms seem more resistant to cold than has been supposed, for the 

 severe cold of the winter of 1901-2, when a temperature of about 13 F., was reached, 

 killed very few of the Saharan date palms in the cooperative garden at Tempe, which 

 were planted in July, 1900. A few of the offshoots set out in 1901 passed through 

 the cold weather without being killed, thanks probably to the protection afforded by 

 wrapping them in several thicknesses of burlap sacking. It is now very clear that 

 large offshoots withstand cold much better than small ones and besides bear the 

 long voyage better. 



&The lowest temperature recorded at Salton is 20 F., with 22 F. at Mammoth 

 Tank, where only 9 out of the 23 years recorded show temperatures below 30 F. 

 At Indio in the northern and at Imperial in the southern part of the basin temper- 

 atures of 18 F. are recorded. At Indio the temperatures are probably lowered by 

 cold winds which blow down from the mountains to the north and west through a 

 valley-like prolongation of the desert to the northwest. The young date palms 

 which grow about Indio without any protection are proof that the winters are not 

 too severe even for very young plants. However, winter cold is the greatest danger 

 to which the date palm is exposed in the Salton Basin, and intending planters should 

 be careful to avoid low, cold situations in setting out date palms, for Snow reports 

 on January 2, 1902, at 8 o'clock a. m., a temperature of 13 F. and ice 2 inches thick. 

 (Bui. 140, Cal. Exp. Sta., p. 45.) A. V. Stubenrauch states that this record is for 

 Imperial, Cal. 



