FROST RESISTANCE OF EUCALYPTUS IN CALIFORNIA 431 



Eucalyptus corynocalyx F. v. M. Sugar Gum 



The efifect of the freeze on the sugar gum varied a great deal with 

 different individuals, even in the same locality and neighborhood. 



The following table shows the general effect of the same tempera- 

 tures in different localities on sugar gum of dift'erent age and size : 



Table 4 



District D. b. h. Height Age Damage Temperature 



Inches Feet Degrees 



Riverside 24 80 18 Moderate 18 



San Bernardino 20 60 14 Moderate 18 



Redlands 12 65 11 Serious iS 



Colton 8 40 . . Serious 18 



Del Rosa 6 3 Serious 14 



All or nearly all of the leaves of the larger trees were killed and 

 many of the smaller twigs. In two instances, near San Bernardino, the 

 leaves on the north and east side of the trees were killed, while those 

 on the inside of the crowns and the other two sides were only nipped 

 slightly at the edges. 



Individual variation in resistance to frost injury was observed in a 

 row of sugar gums in Riverside. Several trees were nearly leafless; 

 some had but few leaves touched by the frost, while still others showed 

 very little damage at all, except for a few injured leaves here and there. 



In the Del Rosa arboretum the tips of all the twigs were killed. The 

 topmost branches were killed back for from 6 to 18 inches, and those 

 in the lower part of the crown for from 2 to 6 inches. Ninety per cent 

 of all the foliage was killed, while the remainder was severely injured. 

 On the larger branches new growth occasionally appeared from adven- 

 titious buds, but, as a rule, on these younger plants the growth was 

 confined to the main stem within 8 inches of the ground. On some the 

 growth came from 2 to 6 inches below ground. Eight per cent of the 

 young trees in the arboretum were killed outright. 



Older trees affected by the low temperature produced sprouts, those 

 hurt most usually developing the largest number. 



On the whole, this species was rather seriously affected by low tem- 

 peratures, the older plants being more resistant than younger ones. 

 The non-injury of a number of plants can only be accounted for by 

 individual variation. 



Eucalyptus Icucoxylon F. v. M. White Wood 



Like the drooping gum, the white wood has not been planted in 

 southern California except at Del Rosa. Five three-year-old trees are 



