Native to the central Rockies of the America West, Colorado blue spruces (Picea pungens var. glauca) make attractive solitary specimen trees for gardens in areas where summers are not too long and hot. While the wild form grows 30 to 60 feet tall and 10 to 20 feet wide at maturity, many cultivated varieties (cultivars) exist today, so you can choose trees that are smaller or have more pronounced blue needle coloring to suit personal tastes. Grow Colorado blue spruces in USDA hardiness zones 2 through 7.
This "old-fashioned" cultivar of Colorado blue spruce is also known as Moerheimii. It bears dense, rich, powdery blue foliage that is about 1 1/2 inches long. It grows with a very upright, pyramid-like shape, but when it's young the plant looks irregularly branched and rather open in habit. It matures 35 to 50 feet tall and 10 to 18 feet wide.
Dr. Michael Dirr of the University of Georgia considers this cultivar one of the best since it develops such a symmetrical, pyramidal shape. The branches are densely cloaked in particularly steel blue needles that appear thick and prickly. Some nurseries sell this selection under synonymous names like Thomsen, Thompson or Thompsenii. It grows 40 to 50 feet tall and 20 feet wide.
The Hoopsii cultivar is a bit slower growing than other upright Colorado blue spruce trees. Its needles are a pale whitish blue, much brighter in the light than others. It attains a dense, pyramid-like shape 30 to 50 fee tall and 15 to 20 feet wide.
When compared to other cultivars, Fat Albert produces slightly short branches and develops a wide, stout skirt of foliage and branches at its base--the "plumpest" looking tree. The needles are rich blue-gray in color. At maturity, it grows 12 to 18 feet tall and 7 to 10 feet wide.
A slow-growing dwarf shrub, Montgomery develops into a broad, cone-like plant 5 feet tall and 3 feet wide. Some plants are very plump and globe-like in form. The dense branches are thickly covered in powdery blue needles.
Also an "old-fashioned" selection of Colorado blue spruce, Koster (also known as Kosterii) produces needles that are silvery blue. In fact, according to the University of Connecticut, Koster is often not favored by horticulturists because of the unpredictability in its mature habit and lack of uniformity among plants in a grove. It grows 40 to 50 feet tall and 15 feet wide.
A dwarf selection, Mrs. Cesarini has green-blue needles that are much greener in color than other Colorado blue spruces. It tends to grow with a flat top, but eventually reaches 6 feet tall and 5 feet wide.
Growing about 15 to 18 feet tall and 8 to 12 feet wide, Mission Blue grows quickly in comparison to most Colorado blue spruces. This tree is much like Fat Albert, but not nearly as wide or densely branched. The needles are a lighter shade of gray-blue-green.
Better adapted to hot summer regions, potentially into USDA zone 8, Foxtail (also called Iseli Foxtail) grows 30 to 50 feet tall and 10 to 20 feet wide. The bluish green needles are shorter at the tips of young branches and eventually lengthen as they age. The visual effect is a tree with foxtail-tipped branches, unlike any other Colorado blue spruce.