18 BULLETIN 153, 17. S. DEPARTMENT OF AGRICULTURE. 



branches, but the leader from year to year seems to develop as 

 commonly from one of the lateral buds as from the terminal one, 

 resulting in a crooked bole. The ash plantations examined have 

 grown too slowly to make pruning a profitable operation, but if 

 especially straight stuff is desired it can be obtained either by very 

 close spacing or by pruning. Ash will grow fairly straight if spaced 

 closely, and pruning should accomplish the same result as close 

 spacing. One method of pruning is to cut off each year the lateral 

 shoots which threaten to compete with the leader; another is to 

 pinch off the lateral buds formed near the tip on the terminal shoot. 



The branches of European larch die early, but are very persistent. 

 Pruning this tree does not pay, however, because the products of 

 the plantation (chiefly posts and poles) are almost, if not fully, 

 as valuable when somewhat knotty as when clear. 



Cottonwood prunes itself exceptionally well, and soft maple, black 

 cherry, and Scotch pine also lose their branches readily. The oaks, 

 as a rule, are not good self-pruners, but they grow so slowly that 

 pruning is not a profitable operation. 



MIXTURES. 



Comparatively few plantations of mixed species have been set 

 out in the region under discussion, and in the few cases where this 

 has been done the mixture has usually proved unsuccessful. This 

 has been due, however, more to the planters' ignorance of the require- 

 ments of the species planted than to any essentail defect in the 

 method itself. A mixture of two or more species is often desirable. 

 Some trees, such as cottonwood and European larch, need to be 

 spaced widely, while others, like black walnut and black locust, 

 have such a scant foliage that they do not shade the ground com- 

 pletely enough to prevent the growth of a heavy sod of grass. In 

 such cases a mixture will more completely utilize the area planted, 

 thus increasing the yield, and at the same time will bring about 

 better forest conditions in the plantation. 



Mixtures are desirable for other reasons. Planting stock of such 

 species as white pine and European larch is expensive, and a less 

 valuable species mixed with the main crop, and removed later in 

 thinnings, will keep down the first cost. If a species to be planted 

 is susceptible to serious insect or fungous attack, as is white pine 

 or black locust, the mixture of another species not susceptible will 

 provide for a stand of trees on the area in case the pine or locust 

 is killed. When such species as European larch, white pine, or black 

 walnut are widely spaced, in order to promote the most rapid 

 growth, it may be advisable to interspace the area with some more 

 tolerant and slower-growing species. 



A number of mixtures are given below which should prove suc- 

 cessful on soils adapted to both species of the mixture, and which 



