TREE-PLANTING ON PRAIRIES. 47 



considered one under twenty feet in height. In Russia 

 and at the Experiment Station at Indian Head, Manitoba, 

 windbreaks of Artemisia tobolksiana, which seldom grows 

 more than eight feet high, are often used. About farm 

 buildings ^^indbreaks cannot be too high, and for this pur- 

 pose the largest, longest-lived trees should be used. 



Kinds of Trees for a Windbreak. In too many instances 

 too many tree-planters on the prairies have put out exclu- 



FiG. 3. — A young White Willow windbreak on dry prairie. Grown 

 entirely by mulching after being well started. 



sively quick-growing, short-lived trees, such as the Cotton- 

 wood and Lombardy Poplar, and after fifteen or twenty 

 years they have found their trees dying and nothing coming 

 on to take their places. The quick-growing kinds are very 

 desirable as a protection for the near future, but they are 

 often short-lived and should never be planted alone. 

 Among them should be planted a sufficient number of 



