Arapaho: nii’ibootou’
English: Colorado blue spruce
Navajo: c’o denini
Shoshone: bah·soo
Spanish: Pícea de Colorado or pícea azul
Natural history
Colorado Blue Spruce is an evergreen tree found throughout the foothill and subalpine forests of the Colorado Rockies from 7,000 up to 11,000 feet where it grows alongside White fir, Ponderosa pine, and Engelmann spruce. The range of Picea pungens extends to the other Four Corners states, as well as Wyoming and Idaho. It often has a conical crown and can grow to over 45 m tall. As its common English name conveys, its foliage tends to be bluish-green in color. Its leaves are short, rarely much more than 2 cm long. They grow singly and unfascicled from twigs and are truly needle-like, as they are quite ridged and sharp tipped compared to the relatively blunt needle tips of other species that might look somewhat similar, such as firs and Douglas-fir. This characteristic becomes quite obvious when attempting to grasp a needled spruce twig. The needles of Colorado blue spruce are often evenly four-sided, a feature which allows them to be easily rolled between thumb and forefinger compared to the flatter needles of fir trees. These squared needles will leave a short peg on the twig when they fall, as opposed to the needles of fir trees, which leave a circular leaf scar and no peg. Its seed cones are pendulous, hanging downward from its branches, and consist of relatively thin scales, which rather resemble the fine scaley bark of its trunk.
A unique aspect of the ecology of Colorado blue spruce is its role in the reproductive cycle of the Cooley spruce gall adelgid (Adelges cooleyi), for which this aphid-like insect relies on both Douglas-fir and species of spruce for various parts of its life cycle. Pertaining to the role of Colorado blue spruce, this insect lays its eggs on branch tips near developing leaf buds, and when the eggs hatch, the emerging nymphs feed on newly developing spruce needles. In response to the saliva of these nymphs, a cone-like gall will develop on the branch of the affected tree. An adelgid nymph will grow and develop within the protection its gall, from which it will emerge in summer to seek out a Douglas-fir tree to complete the next stage of its life cycle.
Human history and use
Picea pungens is the Colorado state tree and is commonly grown commercially as a Christmas tree, plantations of which can be found throughout its native range. Indigenous cultures have used spruce trees in manners similar to those of pines for the treatment of respiratory ailments and wounds, as well as for various ceremonial purposes.
References:
Ackerfield, J. 2022. Flora of Colorado. Fort Worth, TX: Brit Press.
Burns, R. M., and B. H. Honkala. 1990. Silvics of North America. Retrieved from Silvics Manual Volume 1-Conifers and Volume 2-Hardwoods: https://www.srs.fs.usda.gov/pubs/misc/ag_654/table_of_contents.htm (2024, November 16)
Forest Health Protection, Rocky Mountain Region. 2011. Cooley Spruce Gall Adelgid. Retrieved from US Forest Service: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5350727.pdf (2024, November 16)
Heil, K. D. et al. 2013. Flora of the Four Corners Region, Vascular Plants of the San Juan River Drainage: Arizona, Colorado, New Mexico, and Utah. Monographs in Systematic Botany from the Missouri Botanical Garden, Vol. 124. Missouri Botanical Garden Press, St. Louis.
Moerman D. E. 1998. Native American Ethnobotany. Portland, OR: Timber Press.
Taylor, R. J. 1993. Picea, pp 369-373 in Flora of North America Editorial Committee [eds.] Flora of North America North of Mexico, Vol. 2. Oxford University Press, New York.
Photo credit:
Photos by Mike Jacob.