70 FARM FORESTRY 



tree for the purpose. Cottonwood will grow 25 feet in five 

 or six years on good soil. Silver maple and box elder are also 

 fast-growing trees. A windbreak can be planted using such 

 fast-growing trees and at the same time a more valuable tree 

 for the purpose can be planted which will take the place of 

 the other trees in time. A single row of trees planted along 

 the edges of fields will give good protection in many regions. 

 The trees should be underplanted so that when they begin to 

 shed their lower branches the smaller trees will fill in between 

 them. The large trees can be pruned of their limbs as the 

 lower trees increase in height. In this way the trees will fur- 

 nish valuable wood product as well as protection from the 

 wind. 



In the Middle West cottonwood is the tree best suited for 

 windbreaks when planted on good, moist situations. It should 

 be planted in belts 125 to 150 feet wide running east and west 

 and should not be cut until about 45 years of age, at which 

 time the trees should be nearly 90 feet high. The belts should 

 be underplanted a few years after the cottonwood is started 

 with some more tolerant tree, such as green ash, red oak or 

 the spruces. On the uplands and on the poorer situations 

 osage orange, green ash, honey locust, Scotch pine and Aus- 

 trian pine can be used. 



On the northern prairies protection is necessary from the 

 cold north winds of winter and the hot, dry, chinook winds 

 that blow from the mountains in early spring. Windbreaks 

 should be planted across the northern and western boundaries 

 of each quarter section and one or two rows planted within, 

 the trees being planted in belts from 60 to 75 feet wide. On 

 good situations Scotch pine, Norway pine, Colorado blue 

 spruce and the Black Hills spruce are recommended, and on 

 the poorer situations western yellow pine, Scotch pine and 

 Black Hills spruce. 



In the Lake States white pine is advised for windbreaks, 

 planted in belts running north and south, spaced 4 by 6 feet 



