16 BULLETIN 327, U. S. DEPARTMENT OF AGRICULTURE. 
inches long (PL V, a) , but usually about 3J inches. They are ripe 
by the middle or end of August, the thin, tough scales spreading 
slightly and shedding their seeds during September. In color the 
cones are a very light yellow-brown and rather shiny. A few of 
the empty cones fall during the first winter, but the majority re- 
main on the trees until late autumn of the second season. The 
small seeds (PI. VI, a) are dull chestnut-brown and have pale 
yellow-brown wings. Seed-leaves of the blue spruce vary in number 
from 5 to 6 (PL V, c). 
The sapwood and heartwood are often very similar in color. 
When distinguishable, the heartwood is pale brownish-yellow to 
light straw color, while the sapwood is nearly white, the smoothed 
surface of both having a silklike sheen. Seasoned wood is rather 
light, weighing about 23 pounds per cubic foot, ranking fifth in 
weight among our spruce woods. It is moderately soft, brittle, and 
with narrow, often exceedingly narrow, rings of growth. Owing 
to the limited supply and the commonly knotty character and other- 
wise inferior quality of the wood, it is the least valuable of all of 
our native species for commercial purposes. It is rarely used, ex- 
cept locally for house logs, corral poles and posts, temporary mine 
props, fuel, and occasionally for railroad ties. 
OCCUEEENCE AND HABITS. 
Single trees, small groups, and scattered pure groves of limited 
size occur along the immediate banks of streams flowing in deep 
and shallow canyons, and in broad, open, grassy valleys. (Map 
No. 4.) Occasionally single trees are found several hundred yards 
away from streams and 200 to 300 feet above the water. The largest 
trees are always found near water. Blue spruce grows in moder- 
ately rich dry to moist gravelly, sandy, or rocky soils, at elevations 
between about 6,000 and 8,500 feet, sometimes ascending to nearly 
10,000 feet. It is associated mainly with Engelmann spruce, alpine 
fir, and occasionally with narrow-leaf cottonwood. 
The light requirements of blue spruce are imperfectly known at 
present, but it is closely similar in tolerance of shade to the Sitka 
spruce, yet much less tolerant than Engelmann spruce, black spruce, 
and red spruce. Seedlings and young trees endure but little shade 
without a material check to their growth, the most vigorous and full 
development occurring only in full light. 1 With top light saplings 
and older trees are able to endure considerable side shade. 
Blue spruce is an abundant seeder, producing full crops of cones 
at intervals of 2 or 3 years. The seed has a rather high rate of ger- 
1 Much disappointment is experienced by those who use this tree for ornament because 
it does not continue to maintain a full, vigorous crown when planted under the shade of 
older trees or in close groups. The best form can be produced only by planting single 
trees, or groups of trees widely spaced, so that they will have full enjoyment of sunlight. 
