The Colorado spruce Picea pungens, also known as the blue or silver spruce, is an upright pyramidal tree with bluish-green to silver-blue needles. This member of the Pine (Pinaceae) family, native to the Rocky Mountains, grows 40 to 60 feet tall. Some specimens of this slow-growing pine have been known to live as many as 600 years in the western United States. It often is used as a specimen tree in the home landscape because of its unique blue coloration. Its sharp needles make it unappealing to deer.
Choose the cultivated variety 'Glauca' when purchasing a Colorado blue spruce. This cultivar is known for the bluest coloration.
Select a Picea pungens 'Glauca' that has been propagated vegetatively. This ensures that it was taken from parent stock with a distinct blue color.
Plant the tree in a location where it will receive at least six hours of sun per day, preferably in sandy, clay or loamy soil. Providing these optimum growing conditions will increase the chances of having a healthy tree with healthy coloration.
Do not fertilize the tree in its first year. Thereafter, apply an organic fertilizer every spring. Dead wood also should be pruned from the tree in the spring.
Apply a chelated iron-rich fertilizer if a blue spruce develops a yellow or yellow-green color. A shortage of iron will cause the needles of a blue spruce to lose their blue coloration. The fertilizer will replace the depleted iron and help the needles regain their blue color.