Colorado Spruce (Blue Spruce)
Picea pungens (PINACEAE)
Planting and Growing Colorado Spruce Trees
You’ll find everything you need to know to plant and grow Colorado spruce or blue spruce trees in the accompanying table’s tabs:
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- Foliage, cones, and seeds of Colorado spruce or blue spruce
- Growing conditions for Colorado spruce or blue spruce
- When to plant Colorado spruce or blue spruce
- How to plant Colorado spruce or blue spruce
- How to prune Colorado spruce or blue spruce
- Watering, fertilizing, and care of Colorado spruce or blue spruce
- Landscape uses of Colorado spruce or blue spruce
- Pest and disease control for Colorado spruce or blue spruce
Growing Colorado Spruce Trees
Several cultivars of medium-growing, upright, pyramid-shaped, coniferous, evergreen trees, to 100 ft. (30 m) tall and 25 ft. (7.5 m) wide, with whorled, nodding branches, and radiating, shiny, silver gray, blue silver, stiff, sharp, round needles, to 3/4 in. (19 mm) long, and with smooth becoming rough, blue gray, resinous bark.
Colorado Spruce Planting and Care Guide
Flowering and Cones
Male cones resemble feathery catkins, to 2 in. (50 mm) long; female cones are blue green, dangling, elongated, and pointed, 3–4 in. (75–100 mm) long, with scales and winged seed.
Best Climates
U.S.D.A. Plant Hardiness Zones 3–8. Hardy. Best in high elevations and cold-winter climates with moderate to low humidity.
Colorado blue spruce is among the most heat- and humidity tolerant species of the Picea genus.
Soil Type and Fertility
Moist to damp, well-drained soil. Fertility: Rich–average. 5.0–6.5 pH.
Avoid planting near roadways, driveways, sidewalks where rock salt is used as a de-icing agent during winter. Salt applications cause high pH soil conditions.
Where and How to Plant
Full sun. Space 12–16 ft. (3.7–4.9 m) apart.
Proper Care
Easy–moderate. Keep moist; allow soil surface to dry between waterings. Avoid fertilizing. Prune to shape in spring, removing half of new growth “candles.” Propagate by cuttings, seed.
About This Species
Good choice for accents, screens, windbreaks in meadow, woodland gardens and open landscapes.
Maturing trees shade underfoliage, causing needle loss and branch death. Needle loss also may occur in heat and humid conditions. Aphid, spider mite, gypsy moth, tussock moth and canker susceptible.
Common Species and Cultivars of Spruce
Spruce Species:
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- Picea abies, Norway spruce
- Picea brewerana, Brewer weeping spruce
- Picea engelmanii, Engelmann spruce
- Picea fraserii, Fraser spruce
- Picea glauca, white spruce
- Picea mariana, black spruce
- Picea pungens, Colorado blue spruce
- Picea sitchensis, Sitka spruce
Popular Cultivars:
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- Picea glauca var. albertiana, Alberta spruce
- Picea glauca var. densata, Black Hills spruce
- Picea pungens ‘Glauca’, blue spruce
- Picea pungens ‘Pendula’, weeping blue spruce
About Spruce Trees
The Picea genus, with its 45 species of firlike, large and stately, pyramid-shaped conifers, is native to the cool, temperate mountains of the northern hemisphere. Spruces can be distinguished from the firs by their large, dangling cones and stiff needles. They are excellent trees for use in full-sun, open landscapes where their tall form and upraised branches may be appreciated.
Spruces are easily recognized in the garden because of their arrow-straight, conical form; whorled branches; rigidly stiff needles; and large, dangling cones. When mature, they have straight, limbless trunks and open crowns, traits that made them the tree of choice for wood used for sailing ship masts throughout the 19th century.
Spruces need mild, moist summers and cold winters to thrive. Avoid planting them in lowland gardens with hot, dry summers and mild winters.
All are medium- to slow-growing trees, eventually reaching 75–150 ft. (23–45 m) tall. Many dwarf cultivars have been hybridized, making them ideal for growing in containers in small-space gardens. When kept rootbound in a planter, they grow slowly and are ideal for bonsai and shape training. They otherwise rarely need pruning.
Spruces are sometimes susceptible to aphids, spider mites, and the larvae of gypsy and tussock moth. They also can contract cytosperma canker, which kills their inner, lower branches.
Choose from among the popularly cultivated species and cultivars, at left.
Planting and Caring for Spruce Trees
Since all landscape trees do best when they are planted in unamended soil, your site should be tested for acid-alkaline balance before planting. Spruces need soils in the 5.0–7.0 pH range; you should choose another conifer if your soil is too alkaline. You also should compare your tree’s needs to your U.S.D.A. Plant Hardiness Zone.
Plant all spruces in moist, well-drained, acidic soil.
Carefully match your planting hole’s depth to the soil line on the rootball of your tree when you plant. Spruces are shallow-rooted trees that need good drainage. Their root crowns should be positioned at the same level as they were grown at the tree nursery.
Backfill the planting hole with native soil, surround it with a moat, and water the tree often through its first two seasons, whenever the soil surface becomes dry. Water established trees in times of drought.
Choose spruces for open or woodland gardens. They grow slowly to become the dominant feature in the landscape, so plant them with ample space, especially near structures or paving.
To use a spruce as an indoor holiday decoration, plant it and its container in the soil, applying mulch over its roots. Unearth the tree before the soil freezes, clean its container, and bring it indoors. When the holiday season is over, the tree can be replanted in your garden.