i8 EUCALYPTUS. 



Report of Byron O. Clark, Eucalyptus sideroxydon, 

 (Eucalyptus leucoxylon) on the side of a zanja at Anahiem. 

 Cut when 4^ years old. Height 71 feet. 



In Dr. Aber's plantations on the Rio de La Plata, Argen- 

 tine the Karri, Eucalyptus diversicolor, grew fastest and 

 Eucalyptus corymbosa ranked with blue gum. 



At from ten to twelve years of age the blue gum in 

 California ceases to maintain its phenomenal fast growth. 

 The other species cease their fast growth, as a general rule, 

 some years sooner. In this matter some ratio seems to 

 exist between the duration of rapid growth and the event- 

 ual height of the tree. 



The blue gum is like all the valuable species of Eucalyp- 

 tus in not being able to stand prolonged or very heavy frost. 

 What it will stand depends something on the humidity, the 

 condition of the tree as to sap flow and the age of the tree. 

 Old trees have withstood a temperature of 15 F. without 

 material injury. Young trees will, however, stand no such 

 temperature. A minimum temperature of 24 may be 

 deemed safe. Von Mueller has noted the blue gum shoots 

 on giant trees along the Dandenong range in Victoria, frost 

 burned, and has also noted these trees covered with snow 

 for long periods without injury. In California, one species 

 of our indigenous Rhus of the disagreeable smelling leaf, 

 what we call the evergreen sumac, is often frost burned in 

 its native haunts. So in the blue gum and the sumac we 

 find imperfect adaptation to their present native conditions, 

 due perhaps to a changing climate. 



This year we have had, in Southern California, nights 

 colder than usual, that is, temperatures that occur once or 

 twice in a decade. After these cold nights I visited two 

 sandy washes along the foot hills, in one of which were 2 



