49 



planted are an advantage when their benefits are considered 

 for a series of years. It ofttimcs happens that low windbreaks 

 are more beneficial than high windbreaks in holding the snow 

 on the land, for the high windbreaks often form a great drift 

 that may remain late in the spring, while the low windbreak 

 nowhere forms a large drift, but spreads the snow for long dis- 

 tances. Professor Budd says that in parts of the great conti- 

 nental plain of Russia, where the climatic changes are much the 

 same as in this section, the use of low windbreaks in wheat 

 fields is very common. 



Height of Windbreak. From the preceding paragraph it 

 will be seen that low windbreaks may often serve a better pur- 

 pose than high ones in protecting fields. Exactly what is meant 

 by a low windbreak may be an open question, but for the pur- 

 poses of this discussion a low windbreak may be 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 windbreaks cannot be 

 too high, and for this purpose 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 exclusively 

 quick-growing, short-lived trees, such as the Cottonwood 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 pro- 

 tection 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 long-lived and perhaps slower-growing 

 kinds, to afford protection in later years, when the short-lived 

 kinds have died out. The soil and location have much to do 

 in determining the longevity of varieties; for instance, the Cot- 

 tonwood and Lombardy Poplar are generally short-lived trees 

 when planted in this section, but when planted in locations 

 where their roots reach the permanent water level their period 

 of life may be considerably lengthened, and they may then even 

 be regarded as long-lived trees. 



In starting a grove or windbreak on the prairie in this sec- 

 tion, there is probably no better tree to begin with than the 



