Native to the central and southern Rocky Mountains, the Colorado blue spruce (Picea pungens var. glauca) attains an upright, cone-like shape. The attractive blue-green to silvery blue needles make it a popular specimen tree or dwarf conifer choice for cold winter areas.
Early Development
According to the U.S. Forest Service, blue spruce trees develop shallow roots after seed germinate, perhaps only 2 to 3 inches deep. This reveals that this tree species grows with a spreading, shallow root system.
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Root Types
Many cultivars of Colorado blue spruce exist today, ranging in mature height from over 50 feet to a dwarf, shrub-like 3 to 8 feet. In all cases, mainly horizontal roots occur, although some mature roots may become larger and grow more deeply to anchor the plant. Do not expect a singular, carrot-like root.
Considerations
If the garden soil is fertile and deep, such as 3 feet, expect Colorado blue spruce roots to still grow more horizontally and broadly across the soil profile, but some deeper roots may penetrate downward. In contrast, a shallow topsoil, only 18 inches atop bedrock such as on a mountain slope, leads to far fewer deeply occurring roots.