BLACK WALNUT! ITS GROWTH AND MANAGEMENT. 
25 
to 150 years at least. The age to which individual walnut trees could 
be best grown, from the standpoint of greatest volume production, is 
probably limited not so much by an ultimate decrease in the rate of 
volume growth as by the setting in of butt rot. The average age at 
which logs are cut at the present time is 80 or 90 years — a period at 
which the tree is making rapid growth. 
Table 5. — Volume growth of black icalnut. 
Average 
Current 
Age. 
Volume. 
annual 
annual 
growth. 
growth.* 
Board 
Board - 
Board 
Years. 
feet: 
feet. 
feet. 
50 
48 
1.0 
60 
100 
1.7 
5.2 
70 
150 
2.1 
5.0 
80 
200 
2.5 
5.0 
90 
260 
2.9 
6.0 
100 
320 
3.2 
6.0 
110 
380 
3.5 
6.0 
120 
440 
3.7 
6.0 
130 
• 505 
3.9 
6.5 
140 
565 
4.0 
6.0 
150 
635 
4.1 
7.0 
1 Average annual growth for each decade. 
RELATION BETWEEN RATE OF GROWTH IN DIAMETER AND THE 
FORMATION OF SAPWOOD. 
The thickness of the sapwood depends very largely upon the 
rapidity of growth, the trees which have grown most rapidly having 
the widest sapwood. For this reason thrifty young trees are more 
likely to have wide sapwood than old trees. Local differences in site, 
however, frequently modify the tendency to vary with rapidity of 
growth. Trees from certain regions are notoriously sappy, but from 
other places the percentage of black heart is uniformly high. The 
relation of rapidity of growth to thickness of sapwood is shown in 
Table 6, which is based on 124 logs from widely scattered points. Of 
those trees in which the rate of growth was about the average the sap- 
wood contained from 12 to 14 annual growth rings. 
Table 6. — Thickness of sapiuood. 1 
Growth 
Thick- 
Years 
Growth 
Thick- 
Years 
Growth 
Thick- 
Years 
last 
ness of 
in 
last 
ness of 
in 
last 
ness of 
in 
decade. 
sapwood. 
sapwood. 
decade. 
sapwood. 
sapwood. 
decade. 
sapwood. 
sapwood. 
Inches. 
Inches. 
Inches. 
Inches. 
Inches. 
Inches. 
0.2 
0.3 
25 
0.9 
1.2 
14 
1.5 
1.9 
13 
.3 
.4 
20 
1.0 
1.4 
14 
1.6 
2.0 
13 
.4 
.7 
18 
1.1 
1.5 
14 
1.7 
2.1 
12 
.0 
.8 
16 
1.2 
1.6 
13 
1.8 
2.2 
12 
.6 
.9 
15 
1.3 
1.7 
13 
1.9 
2.4 
12 
.7 
1.0 
14 
1.4 
1.8 
13 
2.0 
2.5 
12 
.8 
1.1 
14 
1 Based on measurements of 124 logs. 
