18 



DIAGRAM FOR PROPOSED WINDBREAK. For average soil and mois- 

 ture conditions in central Iowa, the following scheme for planting is 

 suggested : 



N 



40 -to 80 rods 



W. 



Russian .olive 

 White spruce 

 White pine 

 White spruce 

 White pine 



White pine 

 Hardy catalpa 

 White pine 

 Hardy catalpa 



FIG. 1. Diagram for proposed windbreak, for average soil and moisture conditions in central Iowa. 



The outer rows should be 12 feet apart and the trees spaced 8 feet 

 apart in the rows. The trees in the inner rows should be planted 6 by 

 6 feet each way, and the catalpa should be removed when large enough 

 for fence posts. 



Russian olive is suggested for the outside row because it is a hardy, 

 low-growing tree, which succeeds under a wide range of soil and mois- 

 ture conditions. It will protect the evergreen seedlings on the interior 

 and will produce a medium grade of fence posts. Russian mulberry 

 may be used in the same way in places where it is hardy. It is not 

 advisable to plant such quick-growing trees as silver maple or boxelder 

 with the slower growing species, for they quickly overtop the more 

 valuable trees and retard their growth by shade, and if they are not 

 removed in time will be a detriment to the windbreak. 



CARE OF YOUNG AND OLD TREES IN THE WINDBREAK. A large pro- 

 portion of the failures of windbreaks is due to a lack of cultivation and 

 care during the first few years. The land upon which the planting is 

 to be done should be well prepared. Growing corn on it for a year or 

 two will put the soil in excellent condition. After the seedlings are 

 planted the ground should be cultivated as long as it is possible to pass 

 between the rows, usually from two to four years. Cultivation should 

 be discontinued by August 1 each year, for it is likely to stimulate new 

 growth which can not become mature before winter. Windbreaks 



[Cir. 154] 



