Colorado blue spruce, also called blue spruce, is a coniferous evergreen tree in the pine family with sharp, short needles, a pyramid shape with silvery-blue foliage color, and commonly used as a Christmas tree. It grows slowly, averaging about 60 feet tall, although some can grow up to 75 feet. A Colorado blue spruce needs regular watering when first planted, 2 inches of garden mulch around the base of the tree to help it retain moisture, enrichment with compost once a year, and six hours of sunlight daily.
|Common Name||Blue spruce, green spruce, white spruce, Colorado spruce, Colorado blue spruce|
|Botanical Name||Picea pungens|
|Mature Size||50-75 ft. high, 15-20 ft. wide.|
|Soil Type||Loamy, clay, sandy, moist, rich, well-drained|
|Soil pH||Acidic, neutral|
|Hardiness Zones||2-7 (USDA)|
|Native Area||North America|
Colorado Blue Spruce Care
Here are the main care requirements for growing a Colorado blue spruce:
- Plant year-round in mild climates; in places with wintery weather and frost, plant in late winter or early spring.
- Place it in a spot with at least six hours of sunlight daily.
- Give it soil that is well-draining with a well-balanced fertilizer or compost-enriched.
- Water regularly in its first year; afterward, only give it water during a drought.
- Locate it at least 20 to 25 feet away from your home since its branches spread out about 20 feet wide.
Plant Colorado blue spruce trees in full sun, ensuring they get at least six hours of unfiltered sun daily to reach their full growth potential. Blue spruce can tolerate some shade, but planting in a low-light area can increase disease incidence and severity.
A spruce tree grows best in a location with moist, well-drained soil made fertile through soil amendments. However, this tree can adapt to loamy, sandy, or clay soils. As for soil pH, spruce thrive between 6.0 and 7.5, but its unfussy nature allows this tree to tolerate highly acidic or alkaline soils.
Once established, this tree is drought-tolerant and can survive periods of low water but thrives with scheduled waterings. During the first season, water the tree regularly to keep the soil moist. Once the tree is established, water it only during dry spells. Avoid waterlogging the tree or creating areas with standing water at its base.
Temperature and Humidity
A native to high mountain areas, Colorado blue spruce, is tolerant of dry, cold weather. However, blue spruce will not thrive in extremely hot conditions, as its needles will turn brown and fall. Still, this tree variety can tolerate heat and humidity better than other spruces.
These trees do not need frequent fertilization. That said, spring fertilization will give the tree an added nutrition boost, likely increasing the needles' length and improving needle color. Sprinkle 10-10-10 slow-release granulated fertilizer over the soil in the root zone. Then, water with about 2 inches of water to prevent fertilizer burn. For fertilizer amounts, follow the product label instructions.
To avoid fertilizer burn entirely, use a natural and pet-friendly option like compost, fish emulsion, cottonseed meal, or alfalfa meal.
Types of Colorado Blue Spruce Trees
The official state tree of Colorado, this slow-growing spruce, is native to the Rocky Mountains, where it was first discovered in 1862. Colorado blue spruce has several varieties, all with beautiful silvery-blue needles:
- Picea pungens "Baby Blue Eyes' is a semi-dwarf cultivar that grows 15 to 20 feet tall.
- Picea pungens 'Bakeri' features a deep blue color and grows 12 to 20 feet high.
- The dwarf variety Picea pungens 'Glauca Globusa' grows 3 to 5 feet high, 3 to 6 feet wide, and rarely produces cones.
- Picea pungens 'Moerheimii' has branches that droop and grows to a maximum of 30 feet tall.
- Picea pungens 'Montgomery' is another dwarf variety that grows 5 to 6 feet high and has dense, blue needles.
Colorado blue spruce has a slow growth rates, growing less than 12 to 24 inches annually. This tree does not need to be pruned but can be if you want denser foliage. In this instance, prune off half of the new growth on each candle (the tip where branch growth occurs each year) in the spring.
Propagating Colorado Blue Spruce
Colorado blue spruce grows well from mid-summer cuttings and is planted in the fall. Cuttings take a while to root (two to three months) and must be treated with a strong rooting hormone. Grow cuttings in cool and humid conditions for successful propagation. Here's how:
- Gather your garden shears, an alcohol wipe, a paintbrush, a potting container, peat, medium-grit sand, 0.6-percent indolebutyric acid rooting talc, and a spray bottle.
- Combine equal parts peat and sand in a bucket. Cover the mix with water and let it sit until the peat swells. After that, fill your potting container with the mixture.
- Clean the blades of your shears with alcohol and cut a tip 4 to 5 inches long from one of the tree's side branches. Make an angled cut between two sets of needles.
- Strip the needles from the bottom half of the cutting and peel the bark from the end. Brush the end with the rooting hormone.
- Poke a hole in the potting container equal to half the length of your cutting. Insert the cutting into the hole and backfill it with the peat mixture.
- Place the pot in a cool indoor spot with filtered light. Avoid direct sun.
- Drizzle water regularly onto the peat's surface, and mist the air above the cutting, allowing the water to fall onto the needles.
- Check for roots after two months (it could take up to four months to root), and then move the pot outside into the direct sun to acclimatize for a week, bringing it in each night.
- Transplant the cutting into the ground in early autumn by digging a small hole, placing the baby tree and the contents of the pot into the hole, backfilling it, and then spreading a thick layer of mulch around the base. Water the tree regularly for three years until it's established.
How to Grow Colorado Blue Spruce from Seed
With patience, Colorado blue spruce can be grown from seed after collecting and drying pinecones to obtain the seeds.
- In spring, soak the seeds in water for 24 hours.
- Wrap the seeds in a moist paper towel and store them in the refrigerator for six weeks.
- Place a seed in a moist seed-starting mixture, cover it with 1/4 inch of the mix, place plastic wrap over the container, and relocate it to a sunny spot.
- Keep the mixture moist until the seed germinates and grows about an inch, then remove the plastic wrap.
- Harden off the seedling by bringing it outside into direct sunlight for several days.
- Transplant the seedling to the ground once it's acclimatized, mulch around the baby tree, and water seedlings regularly for three years.
Colorado blue spruce is native to cold climates; therefore, established trees do not need special care in the winter, as the tree will go dormant during this season. To protect the tree against hungry animals, you can wrap its trunk in burlap.
Mulching around the tree's base helps it retain moisture, prevents soil compaction, and allows roots to stay warmer in winter and warm up faster in spring, extending its growing season.
After a heavy or wet snowfall, shake the branches to prevent them from snapping due to the snow's weight.
Common Pests & Diseases
The most common issues affecting Colorado blue spruce trees are fungal tip blight, fungal needle cast, beetle kill, aphids, the spruce spider mite, Cooley spruce gall adelgid, and canker. On the plus side, Colorado blue spruce trees are deer resistant.
The fungal issues will cause the needles to grow yellow blotches, needle drop, dieback, and sticky tips. This tree can also be affected by Cytospora canker. This fungal disease typically moves into trees that are 15 to 20 years old, causing the needles to turn brown and drop from the branches. Cytospora canker is a stress-induced disease, so manage it by amending the soil regularly and not overwatering.
Signs of spider mite insect activity include a cotton-like substance on the spruce's branches. Another insect, the great spruce bark beetle, regularly affects wild spruce trees. This beetle can take full stands of trees by tunneling into the trees' bark and laying eggs. The holes weaken the tree, eventually causing a die-off.
To ward off pests, hire a company to spray the tree with a non-toxic horticultural oil that won't endanger birds, pets, or humans.
Common Problems with Colorado Blue Spruce
An established Colorado blue spruce tree is usually easy to maintain. Since blue spruce trees need regular watering during their first several years, a common mistake is giving frequent water after the first three years, which can lead to overwatering.
Browning Needles and Die Off
Signs of overwatering include browning needles, wilting branches, and die-off. Never let the tree sit in standing water, and provide ample mulch to keep moisture around the tree's base, which helps the tree between waterings and drought periods.
Red or Purple Needles
If you notice needles turning purple, red, brown, or dead leaves in the spring, it's likely the result of winter injury. Winter injury is often caused by stress; in many cases, it could be underwatering or drought conditions. If you live in a place with wintery weather, do not plant blue spruce in the fall since it does not give the tree enough time to establish its roots properly to brace for the winter weather.
Bottoms Appears to Be Dying
Spruce decline is a term for a dying spruce tree that usually will not recuperate due to one of several factors. This condition is often caused by temperatures that are too high, high humidity, low air circulation, too much moisture on the needles or in the soil, fungal diseases, or insect activity.
You can attempt to revive the tree by correcting the issue affecting the tree—often disease or insects. Some fungicides might effectively treat needle cast disease over the long term but can only protect new growth (it will not revive old growth). Canker diseases are rarely repaired with fungicide; removing the affected branches is usually the best way to stop the spread of that disease.
How fast do blue spruce grow and how long lived are they?
Blue spruce is a long-lived tree with a slow growth rate, growing about 1 to 2 inches annually. They mature at about 20 to 30 years when they produce seeds. On average, they can live up to 200 years, although some specimens have been found that are about 600 years old.
What are the pros and cons with Colorado blue spruce trees?
The great thing about blue spruce trees is they are usually long-lived, make great Christmas trees, and serve as a sturdy windbreak and privacy screen. The biggest disadvantages are its susceptibility to fungal diseases and several types of insects that infest spruce trees.
Are Colorado blue spruce trees messy trees?
Colorado blue spruce trees are not messy trees in the fall, besides some usual needle drop; you don't have to worry about cleaning up after these trees.
How is Colorado blue spruce used in landscaping?
Colorado blue spruce trees are seen planted in rows to form windbreaks or as a "living wall" privacy screen, but they are equally used ornamentally as specimen trees in backyard landscapes.
Blue Spruce: Common Health Issues in the Landscape. University of Massachusetts Amherst Extension Landscape, Nursery and Urban Forestry Program.
Blue spruce. U.S. Department of Agriculture and Natural Resources Conservation Service.
What is spruce decline and what should you do about it? Christmas Trees.