The Colorado Blue Spruce produces a magnificent sight of silver, blue green foliage. This highly durable tree features a pyramidical form that can add interest to any garden and create an attractive boundary to your outdoor space.
Colorado Blue Spruce
Colorado Blue Spruce or Picea pungens displays a beautiful silvery blue green foliage all year round. It features stiff, prickly needles and yields cones up to 4 inches long that hang from the branches, concentrated within the upper crown. Colorado Blue Spruce trees can grow to an impressive 130 feet high with branches that can spread up to 39 feet wide. While it is one of the slowest growing variants of spruce, its massive size on maturity allows these trees to be used as a screen or windbreak in any outdoor space. With minimal care and attention, you can expect your Colorado Blue Spruce to live for 200 years or more.
The Trunk and Branches
Like most spruce varieties, the Colorado Blue has a central trunk and lateral, ascending branches. The bark has a light brown or gray color supporting foliage of silvery blue needles and brown cones.
Colorado Blue spruce trees have individually attached, prickly needles that create a beautiful foliage that varies in color from silver blue to green throughout the year. This can create a stunning feature for your landscaping design.
Uses in Your Garden
While it is slow growing, the Colorado Blue can reach an impressive size, making it an ideal feature in landscaping designs and to act as a boundary fence, screen, or windbreak.
You should avoid planting Colorado Blue too close together or too close to your home to allow sufficient space for growth. With pruning, you can create a perfect pyramidical shape that will add interest to your garden.
Like most spruce varieties, the Colorado Blue requires little maintenance and can thrive in many types of soil and in most climate zones.
Colorado Blue spruce trees can tolerate partial shade through to full sun, but the optimal conditions are full sun with at least six hours of direct, unfiltered sunlight each day. If you plant in a position for full sun, you should maintain optimum soil moisture levels to avoid drying out.
Colorado Blue spruce trees adapt well to many types of soil. It can grow well in loamy, moist, sandy, acidic, rich, or clay soils. The best soil conditions are well drained, moist, and fertile soil. It is not fussy about soil pH levels, but it may perform better in neutral pH soil. In the wild, Colorado Blue spruce trees grow at higher elevations in rocky soil, so providing the soil is well draining, your Colorado Blue should flourish and avoid root rot.
Colorado Blue is very tolerant of drought conditions and can survive in spells of low water. You should avoid water logging as it may not cope well with standing water. During the first season, you will need to water regularly to keep the soil moist, and you may need to give your Colorado Blue a little water during dry spells. It is also a good idea to add a layer of organic mulch to maintain optimum moisture levels. Just ensure that the mulch is pulled a couple of inches from the base of the tree trunk to avoid rot.
Established Colorado Blue spruce trees have excellent winter hardiness and are tolerant down to temperatures of -40ºf. This extreme temperature variance makes this tree ideal for growth throughout the year. It is resistant to harsh winter conditions and is not susceptible to winter injury.
According to American Horticultural Society data, the Colorado Blue has a Heat Resistance rating range of zones 3 to 7. This is based on the average number of days at temperatures above 86ºf per year.
Pests and Diseases
Colorado Blue spruce trees are resistant to most diseases and pests, but there are some possible issues that include:
Lirula Needle Blight: This can cause graying of the needles and in some cases of infection, black bands across the affected needles.
Cytospora Canker: This is a fungal disease affecting older spruces. The symptoms include brown needles and a white residue caused by resin oozing from infected areas of the tree. Affected branches need to be pruned off during winter, as there is no chemical treatment for the disease.
Needlecast: This is the name common for a variety of fungal diseases. Needlecast causes the tree to shed its needles, and new shoots are often infected. The infected needles don’t die off until the following year, so it can create an outer layer of live needles that surround dead inner needles. This requires fungicide treatment to protect new growth, but it will not revive any dying branches.
White Pine Weevils: These weevils are a leading cause of die back. You need to cut off any dying leaders before the damage can reach the first ring of any branches, and you should choose another branch as a leader. The new leader will need to be trained by staking it into an upright position.
Colorado Blue spruces do not need regular, frequent fertilization. If you want to give your tree a nutrient boost, you can do this before spring to improve the needle color. The best option is to use slow release granules in the root zone. You should add water to incorporate the fertilizer and prevent fertilizer burn.
Pruning and Trimming
Generally, Colorado Blue do not need pruning, but if you want to promote a denser foliage, they can be pruned. You should remove any broken, competing, dead, or diseased branches, just after the branch collar, close to the trunk. Shape the tree according to its natural taper. The crown is the narrowest point, and it is widest at the bottom, so you should work from the top down. It is not recommended to prune over one quarter of the total crown in a season as it can cause shock that can encourage disease. You should also avoid cutting the top off the tree as this can lead to disease and decay.
The Origins of the Colorado Blue Spruce
The Colorado Blue Spruce tree was discovered growing in meadows and beside streams high in the Rocky Mountains in 1862. It was officially named in 1879 by George Engelmann. Once discovered, the fame of this beautiful tree quickly spread, and today is one of the most widely planted trees for landscaping. According to Montreal Botanical Garden curator emeritus, Henry Tuescher, the Colorado Blue is one of the five finest conifers. It was adopted as the Colorado state tree in 1939, a massive delay after Colorado school children voted for the Blue to be the state tree in 1892. The Colorado Blue is also the Utah state tree.