A coniferous tree, the Colorado blue spruce (Picea pungens) was first seen by pioneers in the Rocky Mountains. As blue spruce varieties can live for over a hundred years, the Colorado blue spruce is used as a foliage accent, a privacy screen in urban environments and as a windbreak. While a hardy tree, Colorado blue spruces often suffer from cankers. To prevent this and other disease from taking root, plant a wide range of conifers, not just Colorado blue spruce. It does best in U.S. Department of Agriculture plant hardiness zones 2 through 7.
The Colorado blue spruce is a slow grower, developing between 6 to 12 inches of new growth each year. In situations where special care is given, the tree can grow upwards of 2 feet each year, according to the Idaho Forest Products Commission. Of note however, is that after they are first transplanted, the blue spruce can grow even more slowly for the first few years, as it gradually adapts to its new environment. In general, Colorado blue spruce will reach a maximum height of 70 feet, although there are documented instances of them growing even taller. In home landscapes, Colorado blue spruce most commonly reaches a maximum height of 40 feet due to space restrictions.
When fully mature, Colorado blue spruce trees can reach a width of 15 feet in diameter. With its top-tapering pyramid shape, the Colorado blue spruce grows about a 1/2 inch a year in diameter. As a very large tree, Colorado blue spruce requires significant spacing for it to thrive. Plant the trees between 15 and 20 feet apart for optimal growing conditions.
For optimum growth, do not plant your blue spruce too deeply. Keep the top of the root stock at ground level, otherwise, the Colorado blue spruce may develop trunk cankers. While mulch will help prevent frost damage, reduce weed growth and keep soil moisture levels steady, keep it at least 4 inches away from the trunk to reduce the likelihood of sores developing. Similarly, do not overwater the tree, and standing water or waterlogged soil can quickly kill a blue spruce.
Cytospora canker is a common disease that will kill Colorado blue spruces prematurely. If you see many brown needles and dead tree limbs with an oozing white liquid, your Colorado blue spruce is likely suffering from cytospora canker. Remove the dead limbs to try and prevent an early death.