Colorado Blue Spruce

Colorado Blue Spruce is hardy in USDA zones 2 through 7. It performs best in full to part sun (at least six hours of direct light keeps the color brightest and the form dense) and in moist, well-draining soil. It tolerates a range of soils but will not thrive in soggy, poorly drained ground.

Planting

1. Choose a site with full to part sun and plenty of open space overhead and to the sides, away from buildings, eaves, and power lines.
2. Confirm the soil drains well; avoid low spots where water collects after rain.
3. Dig the hole twice as wide as the root ball but no deeper than its height.
4. Set the tree so the root flare (where the trunk widens into the roots) sits right at ground level. Do not bury the flare.
5. Backfill with the native soil, firm gently to remove air pockets, and water in deeply to settle the roots.
6. Spread two to three inches of mulch over the root zone, keeping it a few inches back from the trunk. For a windbreak row, space trees roughly 15 to 25 feet apart so each tree has room for its wide mature spread; tighter spacing will cause crowding and bare, shaded lower branches over time.

Care & maintenance

• Water. Water deeply and regularly through the first one to two years while roots establish. Even mature trees benefit from a deep soak during droughts and in dry fall weather before the ground freezes, which helps prevent winter needle desiccation.
• Feed. Apply a light, slow-release evergreen or conifer fertilizer in early spring. Avoid heavy feeding, which forces weak growth.
• Light. Give it full to part sun. The bluest color and densest form come from a bright, open location.
• Prune. Blue spruce needs little pruning and looks best left to its natural pyramid. If you must shape it, trim only the green outer growth in spring. Never cut back into bare, leafless inner wood, spruce will not regrow from old wood and the cut stays bare permanently.
• Spacing. For a windbreak or screening row, set trees about 15 to 25 feet apart to accommodate the wide mature spread and keep lower branches full.
• Pests & disease. Watch for spruce spider mites in hot, dry weather (look for stippled, fading needles and fine webbing) and for needle cast diseases that cause inner needles to brown and drop, often worse on stressed or overcrowded trees. Good air circulation and proper watering are the best defense.
• Winter care. Mature trees are very cold-hardy. On young trees in exposed sites, gently brush heavy wet snow off the branches to prevent bending and breakage.

How big does a Colorado Blue Spruce get?

At maturity it reaches roughly 30 to 60 feet tall and 30 to 70 feet wide, growing as a broad, symmetrical pyramid. It is a large landscape tree, so give it open space rather than tucking it close to a house or fence line.

How fast does it grow?

Blue spruce grows at a moderate rate, typically adding around a foot or so of height per year once established. It is a long-term investment tree that rewards patience with decades of dense, colorful structure.

How far apart should I plant them for a windbreak or screen?

Because the mature spread is so wide, space trees about 15 to 25 feet apart for a windbreak or screening row. Crowding them closer leads to shaded, bare lower branches and more disease pressure as they grow into each other.

Is it deer resistant?

Yes, relatively so. The stiff, sharp needles make Colorado Blue Spruce one of the more deer-resistant conifers. No plant is completely deer-proof under heavy browsing pressure, but it is rarely a deer's first choice.

Does it stay blue and evergreen all year?

Yes. It holds its needles and its silvery-blue color year-round, including through winter. New spring growth often emerges the brightest blue, and color intensity can vary somewhat from tree to tree.

Why is my blue spruce turning brown?

Browning usually points to one of a few causes:

• Drought or winter desiccation. Dry soil in summer or a dry, windy winter can brown the needles; deep watering, especially before the ground freezes, helps.
• Spruce spider mites. Stippled, dull, fading needles with fine webbing in hot, dry spells signal mites.
• Needle cast disease. Inner and lower needles that brown and drop, often in bands, can indicate a fungal needle cast, worsened by crowding and poor air flow.
• Normal needle drop. Some shedding of the oldest interior needles each year is natural and not a cause for concern.