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Leaves
(needles) are 1-1 1/2 inches long on lower branches but somewhat shorter
on upper branches. They are 4-sided and have a very sharp point on the
end. It is this point which gives the species its name "pungens", from
the Latin word for sharp as in puncture wound. Needles are generally dull
bluish-gray to silvery blue and emit a resinous odor when crushed. Some
trees have a more distinct bluish-white or silvery-white foliage. The cultivated
variety 'glauca' is noted for this type of coloration. Nursery managers
also select for "shiners" which demonstrate this very desirable characteristic.
Needles occur on small peg-like structures on the twig called sterigmata.
The sterigmata persist on the twigs after needles have fallen, which is
usually after the third or fourth year.
Both male and female flowers
(strobili) occur in the same tree, although in different locations. Pollination
occurs in late spring and cones mature in one season. In the fall, cones
are 2-4 inches long and turn chestnut brown with stiff, flattened scales.
Cones generally persist on the tree for one to two years after seed fall.
The bark is thin becoming
moderately thick with age. It is somewhat pale gray in small flattened
scales when young, then turns reddish brown and furrowed with age. |
Blue spruce is moderately
shade tolerant and grows best in deep, rich, gravely soils, often along
stream banks and other sites with high moisture levels. It usually does
not occur in large stands but is found in small groves or in association
with Douglas-fir, lodgepole pine, Engelmann spruce or ponderosa pine. A
deep penetrating root system makes the species resistant to being blown
over.
Major pests include the western
spruce dwarf mistletoe, spruce bark beetle, and spruce budworm. Trees infected
with mistletoe typically develop abnormal masses of branches called "witches
brooms". With severe infestations, trees may be killed.
Blue spruce is finding increasing
popularity as a Christmas tree as a result of its symmetrical form and
attractive blue foliage. The species has an excellent natural shape and
requires little shearing. Additionally, needle retention is among the best
for the spruces. Its popularity as an ornamental leads many consumers to
use blue spruce as a living Christmas tree, to be planted after the holiday
season.
Range:
Blue spruce occurs naturally
from western Wyoming and eastern Idaho southward through central Colorado
and Central Utah. The southern limits are New Mexico and Arizona. It occurs
at elevations of 6,000 to 11,000 feet; generally at higher elevations in
the more southern areas.
Propagation:
Most propagation is by seed
but blue spruce can be grafted or grown from rooted cuttings. Vegetative
propagation is more often used to perpetuate the rarer, more desirable
forms of the species. Picea abies or Picea pungens are preferred rootstock
for grafting.
Over 70 cultivated varieties
have been named.
Uses:
The wood is light to pale
brown in color and is lightweight, soft, and brittle. The lack of natural
pruning leads to boards often being full of knots. Blue spruce grows in
relatively inaccessible locations leading to its not being commercially
important as a timber species. The wood is suitable, however, for posts,
poles, and fuel.
Blue spruce has limited value
to wildlife but does provide cover and seeds for squirrels, rodents and
some birds.
Credits:
REAL TREE CARE
(http://www.realchristmastrees.org)
Prepared by Dr. Craig
R. McKinley, North Carolina State University |
