16 BULLETIN 1060, U. S. DEPARTMENT OE AGRICULTURE. 
LIGHT REQUIREMENTS. 
Sitka spruce, unlike other spruce, is somewhat intolerant of shade. 
Compared with its associates, it is less tolerant than western hem- 
lock and western red cedar and about as tolerant as Douglas fir. 
Seedlings can endure heavy shade and on old burns and logged-over 
areas establish themselves with little difficulty under the dense cover 
of deciduous brush, such as salmonberry and huckleberry, and of 
other coniferous seedling growth ; but strangely enough Sitka spruce 
is seldom found under the heavy canopy of a mature stand. Here 
temperature, not tolerance, is thought to be the governing factor, 
and the coolness in the mature stands prevents, whereas the warmth 
in the openings permits, the germination and establishment of spruce 
seedlings. As the tree advances in age it demands overhead light, 
and dies if long overtopped. 
The dead side branches, which are often moss-covered stubs 2 or 3 
feet long and characteristically coarse and stiff, are very persistent 
in young spruce. The shedding of the dead limbs and cleaning of 
the bole starts when the trees are about 50 years old and often is not 
completed for a century or more, (PL XII and PI. XIII (fig. 1.)) 
REPRODUCTION. 
SEED PRODUCTION AND DISSEMINATION. 
Sitka spruce is a prolific seeder. Open-grown trees commence to 
bear seed at 35 years of age, and trees of all sites are vigorous pro- 
ducers of seed until maturity. Some seed is produced each year 
and heavy crops are yielded every three or four years. The cones 
mature in the early fall of the first year and, under normal condi- 
tions, open and release the seed within a short period afterwards. A 
mature tree with a full crown may produce, in a good seed year, 4 to 
6 bushels of cones, which yield from 0.65 10 to 1.25 X1 pounds of clean 
seed. A pound of these seeds will number between 200.000 and 300,- 
000. Because of their small size and relatively large wings they are 
often carried by the wind 400 feet or more from the base of the tree. 
Many of the seeds filter into the deep duff of the forest floor and are 
stored, their hard covering keeping them viable for several years. 
The seed has a high percentage of germination. In tests 12 of fresh 
commercial seed under greenhouse conditions, this amounts to 72 per 
cent, and is higher than the germination percentage of western hem- 
lock, western red cedar, and Douglas fir as determined in similar tests. 
10 " Sitka Spruce in Alaska," by B. E. Hoffman. Forest Service manuscript report, p. 9 
1912. 
11 " Reforestation on the National Forests," by C. R. Tillotson. TJ. S. Dept. Agr. Bull. 
475, p. 17, 1917. 
13 " Seeding and Planting," by J. W. Tourney, p. 122, 1916. 
