16 



Farmers' Bulletin 1123. 



Occasionally, dead branches of black walnut trees persist for a num- 

 ber of years, and they are likely to form loose knots. The same is 

 true of catalpa, which, moreover, is subject to serious attack by a 

 fungus around the base of these loose dead branches. Such branches 

 of both species should be removed. If, because of wide spacing or 

 for some other reason, the trees are assuming a poor timber form, it 

 may be necessary to correct the condition by pruning. 



If pruning is undertaken it should be conducted during late winter 

 or early spring, and should not be overdone. 



If a tree is pruned too far up, it may become top-heavy and be 

 easily broken off by a severe wind. Catalpa, ash, and black cherry 



FIG. 10. Blue gum ( Eucalyptus globulus) windbreak, sheltering a lemon orchard. San Bernardino 



County, Calif. 



in plantations are known to have suffered from this, and it seems 

 likely that the same thing is true of many. other species. 



PROTECTION. 



Plantations should be protected against fires and grazing. Fires 

 will kill young trees and injure old ones. Live stock of all kinds 

 should preferably be excluded from a plantation at all times and 

 particularly when the trees are small. The animals almost invariably 

 cause damage to the trees by nipping off the branches, peeling the 

 bark, trampling the roots, or trampling the small trees themselves. 

 If the shade of the trees is a necessity for the animals, they should 



