Picea pungens or commonly called as Colorado blue spruce or blue spruce is a broad, dense and pyramidal tree with strong branches that are horizontal to the ground. Picea pungens is an evergreen tree that normally grows to the height of twenty five to thirty feet in landscapes and the diameter of the trunk normally spreads around 1.5m. The bark of tree is thin and scaly and has needle like trees that are 15-30mm long that are stout and rhombic with a dull gray green to bright gracious blue color. These are not fast growing trees, and the needles are soft in the beginning and slowly turn pointed sharp making it difficult to touch. This tree is native to New Mexico, Utah, Arizona, and Colorado.
The leaves of the tree do not fall or have color change during winters. The tree has flowers that are around 2 inch long with beautiful blue, purple, and orange colors. The flowers of the tree are inconspicuous and bloom during springs. The shape of the fruits of this tree is normally oval and elongated to the extent of 3 to 6 inches in length. They are brown in color and do not attract wildlife. The branches of the tree droop as the tree grows and hence they require proper pruning or pedestrian cleaning. The tree required adequate sunlight to grow; it can also grow in a place where there is partial sunlight. Colorado blue spruce can tolerate clay, loam, acidic, occasionally wet, sand, alkaline, and well-drained soils. The tree can tolerate moderate drought conditions.
There are a number of cultivars for the Colorado blue spruce, and the most common cultivar is Glauca. The other cultivars are Argentea, silvery foliage color, Glauca procumbens, Globosa, Hoopsii, Islei Foxtail, Moerheimeii, Pendens and Thompsoni all available in the nurseries.
The plant is vulnerable to pests and infections. Two gall-forming insects are the common invaders of the plant that attack spruce. These galls develop pineapple like galls at the base of the twigs, which look like miniature cones at the branch tips. A few galls on the trees would not cause any harm, however, a serious infestation might kill the plant. In the northern areas, the larva of the spruce budworm originates on the young needles. Mites cause serious infestation during the summer and the dry season after summer. These are tiny and are not visible to the naked eye. The symptoms of the color change on the needles to yellow indicate the symptoms of the mite’s infection on the plant.
Cytospora canker is the most dangerous infection of the plant that might lead to death of the plant. The disease is first noticeable on the older trunks and then spreads to the entire tree. When the tree is infected, the color of the needles turn from brown to reddish brown and are dropped out eventually. White resin patches are easily visible on the infected branches of the tree. Hence, in order to protect the tree from hot as well as extreme cold climates you need to take proper care of the tree.