Evergreen Colorado blue spruce (Picea pungens) has a narrow, pyramidal habit made up of horizontal branches lined with green, bluish-green or silvery-blue needles. It generally grows to a mature height between 30 and 60 feet, though in the wild it can tower up to 100 feet. Colorado blue spruce needs specific conditions to thrive and is quite susceptible to spider mites.
Young Colorado blue spruce trees have a naturally dense, pyramidal habit that may stay pyramidal or may become conical as the tree ages and the lower branches begin to sag. University of Florida IFAS Extension recommends pruning the lower branches on older trees to allow clearance beneath the canopy. Young trees can be shaped lightly to encourage a denser habit. Though Colorado blue spruce has somewhat shallow roots, the roots rarely break the surface enough to become problematic.
2. Where to Plant
A native of the southern Rocky Mountains, Colorado blue spruce does best the in cool climates of U.S. Department of Agriculture plant hardiness zones 2 through 7. The tree prefers full sun, though it will tolerate light shade. The tree is tolerant of strong winds but does poorly in exposed coastal areas, notes Plants for a Future. Colorado blue spruce needs plenty of space to stretch out, so provide at least 10 to 15 feet between each tree if you're planting several of them.
The adaptable Colorado blue spruce will grow in a range of soil conditions, though the ideal soil is well-draining and moist with a pH between 4 and 6. Colorado blue spruce is fairly drought-tolerant once established, but young trees need frequent watering for at least a year after to transplanting to help them form a healthy root system. If young trees are not watered during periods of drought, branches and tips may die or the tree may die, advises Ohio State University. Cytospora canker may affect water-stressed trees of all ages.
Colorado blue spruce may have problems with spruce mites -- tiny foliage-feeding insects that can cause needle drop and branch dieback. To check for mites, hold a piece of clean white paper under a potentially infested branch and strike the branch against the paper to see if any small dark mites are present.