FROST RESISTANCE OF EUCALYPTUS IN CALIFORNIA 415 



An average of these readings indicates a temperature of about 15 

 degrees above zero F. in the general locahty covered. 



EFFECT OF FREEZE IN DIFFERENT SPECIES OF EUCALYPTUS 



The effect of the freeze upon the eucalyptus was as noticeable for 

 the most part as upon the citrus trees. The gums and pepper trees 

 looked like oak or beech trees in late fall. Many persons thought the 

 trees dead because they found no moisture in the bark and the leaves 

 were dry and brown. On this evidence a number of groves were cut 

 down. At the present time, however, the citrus, gum, and pepper trees 

 alike have leafed out, and many show no sign other than dead branch- 

 wood of the exceptional cold they underwent. 



Table 3 summarizes the effect of the low temperatures on the diff'er- 

 ent species of eucalyptus of various ages in the San Bernardino Valley. 



BEHAVIOR OF DIFFERENT SPECIES 



Bucalyptus globulus Lab. Blue Gum 



Blue gum has been more widely planted, both for shade and orna- 

 mental purposes and for timber and windbreaks, than any other species 

 of eucalyptus grown in the United States. In the nursery blue gum is 

 very sensitive, but becomes hardy with age, though it never attains the 

 degree of frost resistance that E. viminalis does. Planted over a wide 

 territory, it caught the lowest temperatures, but not a single tree was 

 found to have been killed by the frost. 



The damage to blue gum seldom extended beyond killing of the 

 leaves. In the case of the coppiced tree the one-year-old sprouts were 

 killed, though the stump was still alive, as evidenced by the new adven- 

 titious shoots. Only one of the coppice shoots was putting forth new 

 growth, which was the case with several trees where the coppice was 

 but one year old. Coppice two years old and older was not killed, 

 though new growth had to be continued by adventitious shoots. 



Dense plantations of blue gum suffered less than more open stands. 

 The leaves on some trees were killed, but in most cases only a fringe 

 of dead tissue was found around the leaf. 



Dense plantations of blue gum suffered less than more open stands. 

 The leaves on some trees were killed, but in most cases only a fringe 

 of dead tissue was found around the leaf. 



Many people, thinking blue-gum trees dead as a result of the freeze, 

 cither pollarded them or cut them down entirely. Trees cut to the 

 ground did not send up very vigorous growth. 



