COMBINATIONS OF .SPECIES FOR PLANTING 



Various combinations of trees may be planted under this system 

 of regeneration from one side, but, as a rule, two or three species are 

 sufficient. If the rows are to be of different varieties, the principal 

 care should be to see that the rapidly-growing hardwoods do not 

 overtop and suppress the slow-growing trees. The intolerant ever- 

 greens, being of slow initial growth, are in more danger of being 

 overtopped than the hardwood trees. 



The following are some of the combinations which might be used: 



Combination No. 1. Rows 8 and 9, white pine; rows 6 and 7, Nor- 

 way spruce; rows 4 and 5, European larch; rows 1, 2 and 3, white pine. 



Combination No. 2. Rows 8 and 9, white cedar or Norway spruce; 

 rows 4, 5, 6 and 7, white pine, red pine or Austrian pine; rows 1, 2 

 and 3, white cedar or Norway spruce. 



Combination No. 3. Rows 8 and 9, European larch (bare in winter) ; 

 rows 6 and 7, white cedar or red cedar;* rows 4 and 5, Norway spruce 

 or white spruce; rows 1, 2 and 3, cottonwood. 



Combination No. 4. Rows 8 and 9, white cedar, Norway spruce or 

 white pine; rows 6 and 7, red pine, Austrian pine, western yellow 

 pine, or Douglas fir; rows 4 and 5, Norway spruce or white cedar; 

 rows 1, 2 and 3, hardy catalpa. 



Combination No. 5. Rows 8 and 9, white pine; rows 6 and 7, Nor- 

 way spruce or white cedar; rows 4 and 5, cottonwood; rows 1, 2 and 

 3, green ash, or Russian mulberry.** 



VARIATIONS IN THE METHOD 



In this first regeneration process, the five-year period between suc- 

 cessive cuttings need not necessarily be adhered to. The period might 

 be reduced to three years or less. In the case of a shelterbelt com- 

 posed of three or four rows of old trees, only one row should be 

 cut at a time, unless the trees are in very poor condition. 



REGENERATION FROM TWO SIDES 



In this method it is also the purpose to secure a new growth of 

 trees without sacrificing entirely the efficiency of the windbreak. By 

 reference to the diagrams in the figs. 6 to 10, it will be noted that 

 instead of a gradual removal of the trees from one side, as was the 

 case in the first method, single rows are taken from each side at inter- 

 vals of five years. The time between the first and the last planting is 

 the same as in the first method of cutting 15 years. 



Figures 6 to 10 show how the cuttings should proceed. In the case 

 illustrated, it is assumed that the shelterbelt is composed of nine 

 rows of trees, most of which will last through the regenerative period 

 of 15 years. 



*Red cedar should not be planted if apple trees are In the vicinity because of 

 fungus trouble. 



**For Southern Iowa only. 



