38 
BULLETIN 55, U. S. DEPARTMENT OF AGRICULTURE. 
COMPARATIVE GROWTH OF SPRUCE AND BALSAM FIR. 
Since spruce and balsam fir nearly always grow together, and any 
plan of management for one species must necessarily include the 
other, a comparison of the growth of the two species is essential. 
In Table 17 is contrasted the average growth in height and diame- 
ter of balsam fir and spruce in the State of Maine. 
Table 17. — Comparative growth, in height and diameter, of balsam, fir and red spruce in 
Maine. 
GROWTH IN HEIGHT. 
Diameter breast high 
(inches). 
Height (feet). 
Diameter breast high 
(inches). 
Height (feet). 
Red 
spruce. 
(Based on 
485 trees.) 
Balsam 
fir. 
(Based on 
456 trees.) 
Red 
spruce. 
(Based on 
485 trees.) 
Balsam 
fir. 
(Based on 
456 trees.) 
1 
14 
21 
28 
33 
37 
41 
44 
48 
12 
20 
27 
35 
42 
48 
54 
60 
64 
10 
52 
55 
58 
60 
03 
65 
67 
68 
70 
68 
72 
75 
78 
81 
84 
86 
2 
11 
3 
12.... 
4 
13 
5 
14 
6 
15 
16 
8 
17..... 
9 
18 
GROWTH IN DIAMETER. 
Age (years). 
Diameter breast 
high (inches). 
Age (years). 
Diameter breast 
high (inches). 
Red 
spruce. 
(Based on 
27 4 trees.) 
Balsam 
fir. 
(Based on 
456 trees.) 
Red 
spruce. 
(Based on 
274 trees.) 
Balsam 
fir. 
(Based on 
456 trees.) 
20 
0.1 
.6 
.8 
1.1 
1.5 
1.8 
2.2 
1.2 
2.7 
4.1 
5.5 
6.7 
7.9 
8.9 
90 
2.7 
3! 2 
3. 7 
4.3 
4.9 
5. 5 
- 9.9 
10.7 
11.3 
11.9 
12.3 
12.6 
12.9 
30 
100 
40 
110 
50 
120 
60 
130 
70.. 
140 
80 
150 
Red spruce grows in height much slower than balsam fir for the 
first 70 years. At a diameter of about 8 inches its rate of growth in 
height is approximately the same as that of balsam fir. At a diame- 
ter of 12 inches balsam fir reaches almost its full height, while spruce 
is still far below its fullest development. From that time on spruce 
continues to grow at a uniform rate for a long period, while the 
growth of balsam fir is rapidly declining until at a diameter of about 
16 inches it practically ceases. 
The same is true of the growth in diameter. At the age of 100 
years spruce is only 3.2 inches in diameter breast high, while balsam 
fir has made nearly two-thirds of its entire diameter growth. After 
