22 



BULLETIN 933, U. S. DEPARTMENT OF AGRICULTURE. 



GROWTH OF INDIVIDUAL TREES. 



Walnut may be classed among the more rapid growing hardwoods. 

 The fertility of the soil on which black walnut is usually found 

 greatly facilitates the growth of the tree. The poorer the site, the 

 slower are all phases of growth, in height, in diameter, and conse- 

 quently in volume. Growth is also affected by the shade from adja- 

 cent trees, and this accounts for the characteristic differences in form. 

 The rate of diameter growth, on soils of equal quality, depends nor- 

 mally upon the amount of foliage, and hence is slower in the small- 

 crowned trees of the forest than in spreading-crowned open-grown 

 trees. When the trees are suppressed by the shade of taller trees, 

 diameter growth is greatly decreased. 



HEIGHT GROWTH. 



Table 2 gives an idea of the average height growth of black walnut 

 in comparatively open, pure stands in central Indiana and Ohio. It 

 should be accepted as applicable only to " grove walnut " : 



Table 2. — Height growth of walnut in comparatively open 

 stands in central Indiana and Ohio. 



Age. 



Height. 



Age. 



Height. 



Age. 



Height. 



Years. 



Feet. 



Years. 



Feet. 



Years. 



Feet. 



10 



13 



60 



72 



110 



84 



20 



35 



70 



75 



120 



85 



30 



53 



80 



78 



130 



86 



40 



62 



90 



81- 



140 



87 



50 



68 



100 



82 



150 



88 



DIAMETER GROWTH. 



In the course of this study diameter-growth measurements were 

 made on 128 trees located at 16 places in 6 States. While the number 

 of trees thus scattered is too small to afford reliable data, the aver- 

 age measurements shown in Table 3 will give a general idea of the 

 average rate of diameter growth, breast high, of walnut under 

 neither the best nor the poorest conditions : 



Table 3. — Breast-high diameter growth of walnut, based on 

 measurements' of 128 trees widely scattered. 1 



Age. 



Diame- 

 ter, 



breast 

 high. 



Age. 



Diame- 

 ter, 

 breast 

 high. 



Age. 



Diame- 

 ter, 

 breast 

 high. 



Years. 

 10 

 20 

 30 

 40 

 50 



Inchex. 



1.2 



5.0 



8.8 



12.5 



15. 7 



Years. 

 60 

 70 

 80 

 90 



100 



Inches. 

 18.3 

 20.6 

 22.2 

 23.8 

 25. 



Years. 

 110 

 120 

 130 

 140 

 150 



Inches. 

 26.0 

 26.9 

 27.8 

 28.5 

 29.2 



1 Distribution of measurements: Indiana, 37 trees from 5 localities; Ohio, 75 trees, 3 localities; Illinois, 

 5 trees, 1 locality; Virginia, 5 trees, 1 locality; New Jersey, 7 trees, 1 locality; Missouri, 3 trees, 1 locality. 



