A planting of blue spruce brightens an otherwise drab January landscape.
Lovelier than any poem, the Colorado (or blue) spruce is one of the most beautiful and admired of all trees. This is an evergreen conifer with a single undivided trunk, occasionally reaching heights of 130 ft (40 m) or more in nature. (Cultivated specimens seldom get more than 50 ft (15 m) tall, with a spread around 15 ft (3 m) across.) With its whorls of horizontal spreading branches, a mature Colorado spruce has a dense, symmetrical crown and is broadly conical in shape. The bark is purplish gray-brown, scaly and develops deep furrows. Young shoots are thick and orange-brown in color. The 4-sided needles are covered with a fine powdery wax that gives them a bluish gray-green color. This glaucous “bloom” can be rubbed off with your fingers. The needles are stiff and acuminate (tips sharply pointed), and about an inch (2-3 cm) long. They curve inward and are arranged radially around the shoots like a prickly bottle brush. The seed-bearing female cones are 3-5 in (8-13 cm) long, erect and green at first, becoming pendant and brown with maturity. The male cones are more like drooping catkins, orange and less than an inch (2.5 cm) long. The spruces are monoecious, with the female cones concentrated on the upper branches, while the male cones are spaced throughout the tree.
More than 40 forms and cultivars have been described. The group (or form) name for all the types with glaucous, blue-gray foliage is P. pungens f. glauca. Important selections in this group include ‘Argentea’ and ‘Koster’, which have silvery blue foliage; ‘Microphylla’, with very short needles; ‘Montgomery’ and ‘Nana’, which are dwarf shrubs to just 5 ft (1.5 m) tall; ‘Thompsen’ and ‘Moerheim’, which are exceptionally blue; ‘Glauca Procumbens’, which grows along the ground; and ‘Glauca Pendula’, which has a graceful, weeping habit. The variety P. pungens var. pungens includes the types that are more green than bluish. Noteworthy selections from this variety include the dull green ‘Viridis’; and ‘Aurea’, which has yellowish foliage.
The foliage of Picea pungens varies from bluish-green to silvery blue and all shades in between. The tan female cones are located at the top of the tree.
Location Picea pungens occurs in the southern Rocky Mountains of Wyoming, Idaho, Colorado, Utah, Arizona and New Mexico at elevations of 6,500-10,750 ft (2,000-3,300 m), often in gravelly soil along stream banks and in moist canyons. Colorado spruce rarely grows in large single species stands, but rather as scattered specimens among other conifers such as Douglas-fir (Pseudotsuga menziesii), lodgepole pine (Pinus contorta), and ponderosa pine (P. ponderosa).
Culture Light:Grow Colorado spruce in full sun, though it can tolerate light shade. The foresters consider Colorado spruce to be of intermediate tolerance to shade.
Moisture: Colorado spruce, which grows naturally in the arid mountains of western North America, is noted for being exceptionally tolerant of dry air. It does not do well in humid locations. Colorado spruce is more tolerant of drought than other spruces, but still should be watered during prolonged dry periods. The soil should be neutral to acidic and moist or dry, but always well drained. A layer of mulch helps to hold moisture and keep the soil over the roots cool.
Hardiness: USDA Zones 3 - 8. Colorado spruce likes it cold. In zones 7 and 8, and following mild winters elsewhere, Colorado spruce is susceptible to damage from the green spruce aphid (Elatobium abietinum), which can completely defoliate otherwise healthy trees.
Propagation: Seed should be sown in spring. Just how blue the needles are varies considerably among seedlings. Growers select the bluest specimens for ornamental planting. Popular cultivars are grafted onto seedling root stock. The dwarf cultivars are propagated from ripe wood cuttings in late summer.
A group of blue spruce provides a visual screen that also absorbs street noise.
The Colorado spruce comes in a variety of forms, colors and sizes. This is a dwarf variety called 'Montgomery'.
With its trim, symmetrical habit and bluish foliage, the Colorado spruce is a favorite Christmas tree. This is an outstanding ornamental conifer widely planted in eastern North America and northern Europe as a formal specimen tree. It is often used as the main focal point in a landscape. Colorado spruces are also useful in shelter belts, wind breaks and living screens. These are slow growing and long lived trees, growing perhaps a foot (30 cm) per year when young, and known to exceed 800 years in age.
Colorado spruce casts a dense shadow and grass will not grow beneath one. Colorado spruce is quite tolerant of exposure to strong and drying winds, salt spray, and to cold, but is susceptible to aluminum toxicity brought about by acid rain. Around Christmas time, smaller specimens are sometimes vulnerable to theft by Scrooge or some other Grinch.
The pale brown wood is lightweight, soft and brittle, and of little commercial value, even if loggers could get up to where the tree grows.
The 45 or so species of spruces (genus Picea) are all native to the cooler, often mountainous, parts of North America, Europe and Asia.