The most common blue evergreen tree or shrub in the landscape is the Colorado blue spruce (Picea pungens). The blue spruce, also commonly known as Colorado spruce or Colorado blue spruce, is a species of spruce tree native to North America in Arizona, Colorado, Idaho, New Mexico, Utah and Wyoming.
Colorado blue spruce (Picea pungens) makes a majestic specimen tree, whether you grow it outdoors or take it indoors as a Christmas tree. This gorgeous tree is low-maintenance. It grows up to 100 feet tall in the wild, and nursery trees reach 60 feet tall. It is often called the Colorado blue spruce because it is found throughout the state, and because it is Colorado’s state tree. Hardy in U.S. Department of Agriculture plant hardiness zones 2 through 8, the blue spruce will live for many years if cared for properly.
In the wild, the Colorado blue spruce can live 200 years or more. In the home landscape, it usually stays healthy for about 40 to 60 years, after which its health begins to fail. Once established, it becomes more drought-tolerant, which allows it to survive in areas with less frequent rainfall.
Picea, the genus name, is thought to come from the Latin word pix meaning “pitch”, a reference to the typical sticky resin in spruce bark. The specific epithet pungens means “sharply pointed”, referring to the leaves. George Engelmann provided the first valid scientific description of Picea pungens in 1879. The most frequently used common name in English is “blue spruce,” which was first used for other trees in 1817. “Colorado blue spruce” was first used in 1912, and “Colorado spruce” dates back to 1881.
This spruce does best in cooler climates and cannot tolerate heat and humidity. It may tolerate the summer weather in the North Carolina mountains. This tree can be grown in average, well-drained soils in full sun, although it will tolerate some shade. It prefers rich, moist soil in full sunlight. Young trees should be kept consistently moist and not allowed to dry out. As this spruce matures, it becomes more drought tolerant and is overall more drought tolerant than other spruces. It has a slow to medium growth rate.
Colorado Blue Spruce (Picea pungens) Distribution
The Colorado Blue Spruce (Picea pungens) is primarily native to the central and southern Rocky Mountains of the western United States. Its range extends from southern and western Wyoming, eastern Idaho, south to Utah, northern and eastern Arizona, southern New Mexico, and central Colorado. It has also been reported in isolated locations in north-central Montana1.
This tree thrives in a climatic zone that is generally cool and humid, with most of the annual precipitation occurring in the summer. The mean annual temperatures where the blue spruce is most commonly found range from 3.9° to 6.1°C (39° to 43°F), with a January mean of -3.9° to -2.8°C (25° to 27°F) and a July mean of 13.9° to 15.0°C (57° to 59°F). The frost-free period from June to August is about 55 to 60 days1.
The Colorado Blue Spruce grows best with abundant moisture but can withstand drought better than any other spruce. It can also endure extremely low temperatures (-40°C; -40°F) and is more resistant to high insolation and frost damage than other associated species.
Characteristics of Colorado Blue Spruce (Picea pungens)
- Growth Habit:
Colorado blue spruce has a dense, pyramidal shape with horizontal branches forming a symmetrical crown. Its stiff, ascending branches give it a strong, architectural appearance. - Size:
It typically grows 30–60 feet (9–18 meters) tall and 10–20 feet (3–6 meters) wide. In its native range, it can reach up to 75 feet (23 meters) under optimal conditions. - Bark:
The bark is gray-brown, thin, and scaly when young, becoming furrowed and flaky as the tree matures. - Growth Rate:
It has a slow to moderate growth rate, averaging about 12–24 inches (30–60 cm) per year under ideal conditions. - Cones:
The cones are cylindrical and measure 2.5–4 inches (6–10 cm) long. They are light green or purplish when young, maturing to a light brown color and hanging downward from the branches. - Foliage:
Its needles are stiff, sharp, and pointed, ranging in color from blue-green to silvery-blue. The blue hue is due to a waxy coating that helps reduce water loss and offers protection from harsh climates. - Lifespan:
Colorado blue spruce is a long-lived species, capable of surviving 200–300 years or more in optimal conditions. - Root System:
The tree develops a shallow yet widespread root system, with the potential for deeper anchoring in loose, well-drained soils. Its root structure makes it somewhat susceptible to drought and windthrow. - USDA Hardiness Zones:
This species is hardy in USDA Zones 2–7, making it well-suited to cold climates and high-altitude environments. - Climate Adaptation:
Native to the Rocky Mountains, Colorado blue spruce thrives in cool, temperate climates with well-drained, moist soils. It is highly tolerant of cold, drought, and urban pollution, making it a popular ornamental tree in landscapes and cityscapes.
Facts About Colorado Blue Spruce (Picea pungens)
The Navajo and Keres Native Americans use this tree as a traditional medicinal plant and a ceremonial item, and twigs are given as gifts to bring good fortune. In traditional medicine, an infusion of the needles is used to treat colds and settle the stomach. This liquid is also used externally for rheumatic pains.
The blue spruce is the state tree of Colorado. It officially became Colorado’s state tree on 7 March 1939 when House Joint Resolution 7 was enacted by the legislature. Previously a vote of the state’s school children was taken on Arbor Day in 1892 expressing their preference for the blue spruce as the state tree.
From 1933 until 2014 the blue spruce was also the state tree of Utah. It was replaced by the quaking aspen because the aspen is a great deal more common than the blue spruce in Utah, making up 10% of the state’s tree cover
Cultivation of Colorado Blue Spruce (Picea pungens)
- Site Selection:
Choose a location with full sun exposure, as Colorado blue spruce requires at least 6 hours of direct sunlight daily. It thrives in open, sunny areas and can tolerate partial shade but with less vibrant foliage. - Soil Requirements:
This species prefers moist, well-drained soils but is adaptable to a variety of soil types, including loam, sandy, and slightly clayey soils. It grows best in neutral to slightly acidic pH levels. - Planting:
Dig a hole twice as wide as the root ball and slightly deeper than its height. Place the tree in the hole, ensuring the root collar is level with the ground surface. Backfill with native soil and tamp gently to eliminate air pockets. - Watering:
Water regularly during the first 2–3 years to establish a strong root system. Mature trees are moderately drought-tolerant but benefit from supplemental watering during prolonged dry spells. - Mulching:
Apply a 2–3 inch layer of mulch around the base to retain moisture, regulate soil temperature, and reduce weed competition. Keep the mulch a few inches away from the trunk to prevent decay. - Fertilization:
Fertilize annually in early spring with a slow-release fertilizer designed for evergreens. Avoid over-fertilizing, as this can lead to excessive growth that weakens the tree. - Pruning:
Prune minimally to remove dead, diseased, or damaged branches. If shaping is needed, do so in late winter or early spring before new growth begins. Avoid cutting into old wood, as the tree does not regenerate from bare stems. - Spacing:
Space trees 10–15 feet apart when planting multiple specimens to allow for proper air circulation and healthy growth, reducing the risk of disease. - Pest and Disease Management:
Monitor for common issues such as spider mites, spruce budworms, and needle cast disease. Maintain good care practices, such as proper watering and spacing, to enhance resistance to pests and diseases. - Cold and Wind Protection:
While Colorado blue spruce is naturally hardy and tolerant of cold, protect young trees from harsh winds using windbreaks or temporary supports until their root systems are well-established.
Blue Spruce Cultivars
- ‘Baby Blue Eyes’: This semi-dwarf cultivar grows slowly but can eventually reach 4.6 to 6.1 meters (15 to 20 ft) in height. It is known for its striking blue-green foliage.
- ‘Bakeri’: A compact cultivar with deeper blue color, it is more compact than the species and has a deeper blue hue.
- ‘Compacta’: This cultivar has a flat-topped shape with long, bright blue, sharp-tipped needles.
- ‘Fastigiata’: It is an upright, semi-dwarf cultivar with blue-green needles, often used as a specimen plant.
- ‘Fat Albert’: Known for its perfect cone shape, closely spaced ascending branches, and steel blue needle color, it is a popular choice for ornamental use.
- ‘Foxtail’: This cultivar has a foxtail-like appearance of new branches, giving it a unique look.
- ‘Glauca’: It features waxy blue-gray foliage, which is one of the main characteristics of the blue spruce.
- ‘Glauca Globosa’: This cultivar has a neat, dense, and compact rounded shape, making it suitable for smaller spaces.
- ‘Glauca Pendula’: Known for its blue-needled, sprawling, and spreading form, it is a unique cultivar for those looking for a more horizontal growth habit.
- ‘Glauca Prostrata’: This cultivar is a shrub form with a dwarf, procumbent shape and blue-green needles, ideal for ground cover or rock gardens.