RELATIVE FROST RESISTANCE OF EUCALYPTUS IN 

 SOUTHERN CALIFORNIA 



By E. N. Munns 

 Forest Examiner, U. S. forest Service 



While eucalyptus in California are in general sensitive to low tem- 

 peratures, widely divergent claims have been advanced regarding the 

 relative frost resistance of the various species based on their behavior 

 in different localities at different times. The observations during an 

 exceptional period of low temperature recorded in this report furnish 

 important evidence regarding the frost resistance of the various species. 



THE COLD PERIOD 



Between January 3 and January 8, 1913, southern California passed 

 through a period of low temperature spoken of locally as the "freeze." 

 The first and second days of January were clear and unusually warm. 

 Temperatures throughout the region ranged between 70 and 90 degrees. 

 The morning of the third the wind changed from the southwest to 

 north. A light, three-miles-an-hour breeze was blowing at 9 o'clock. 

 From this time on up to the middle of the afternoon the wind increased 

 in velocity until a speed of 35 to 50 miles an hour was reached. 



Like the preceding day, January 4 was clear, but the temperature 

 did not increase perceptibly throughout the day. The next day the 

 wind again increased in violence and power. Trees were uprooted in 

 exposed situations. During this day the temperature remained about 

 the same, with a drop toward evening. In places in the orchards ice 

 formed within a foot of the burning oil in smudge pots. 



In 1900 and again in 191 1 low temperatures prevailed in this region, 

 but in these years the cold was not as severe as during the winter of 

 1913. In the interval between December 29, 1900, and January 4, 1901, 

 the temperature did not get below 18 degrees anywhere in the San Ber- 

 nardino Valley, and during the Christmas season of 191 1, 19 degrees 

 was the lowest temperature recorded. Weather Bureau records in this 

 portion of the State do not show another such low temperature period 

 since instruments have been installed in the region, nor can the oldest 

 inhabitant recall its equal. The north winds swept down upon the 

 valley through the passes in the mountains and made useless all the 



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