|Colorado Blue Spruce
Picea pungens Engelm.
Colorado blue spruce, or blue spruce, is an attractive tree often used for Christmas trees or as ornamentals, particularly in the eastern United States and Europe. It is the official state tree of both Colorado and Utah. The species generally reaches a height of 65-115 feet at maturity with a diameter of 2-3 feet. It has a narrow, pyramidal shape and cone-shaped crown. As trees become older, they often take on a more irregular appearance. While blue spruce grows relatively slowly, it is long-lived and may reach ages of 600-800 years.
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.
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 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.