Pest alert – Colorado Blue Spruce Issues

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The Colorado Blue Spruce is a beautiful tree. Its blue/gray color, conical shape, and erect stems make this specialty conifer a popular plant. However, I see many of these trees dying locally.

ideally sited co blue spruce

This is an ideally sited Colorado blue spruce; high altitude around 3000 feet, full sun, well drained soil, and plenty of air circulation.

Should you invest in a Colorado blue spruce? First of all, these trees are meant to be in Colorado at high elevations enjoying cool, flowing air and low humidity. It stands to reason that they would suffer in small yards surrounded by woods when the temperatures are near 90 degrees and the humidity is 85%. It is too hot, humid, wet, and shady for the trees in much of Western North Carolina.

Blue spruces like dry, sunny, windy environments. They are from Colorado, Utah and the southwestern states where they get very little rain. Our humidity is too much for them and most of us have too much shade and not enough air circulation for them. They eventually get needle cast fungus which makes the needles fall off.

Colorado blue spruces grow great at high elevation above 4000 feet. Hendersonville is at 2100 feet. This is why Christmas tree farms do not work here. We must go into the higher elevation around Boone, NC to grow Christmas trees.

Below 4000 feet Colorado blue spruce trees suffer from drought and heat. However they need full sun and suffer in the shade. Most suburban yards are too shady locally.
Colorado blue spruce also needs dry air. Fungal diseases such as needle cast can occur when leaves stay wet too long. High humidity leads to disease.
These trees are also attacked by spider mites. These microscopic arachnids suck the life out of the plant. Spruce are very susceptible to spider mites.
spruce decline

Spruce Decline is a term for the slow death of Colorado blue spruce and other specialty conifers due to high temperatures, high humidity, low air flow, excessive leaf and soil wetness, fungal diseases, and spider mites.

Colorado Blue Spruce needs air circulation. Air movement dries leaves. Moving air also helps reduce spider mite populations.
Soils that are too warm can also stress these trees. Our soils are much warmer here than in the high altitudes of Colorado. Mulch can help cool soils locally.
Trees nearby outcompete Colorado blue spruce for water. They also shade the needles making them stay wetter longer after a rain. The shadier an area, the worse the trees perform.
poorly sited dwarf spruce

These dwarf spruce are in too much shade. Often the trees will lose needles on the shady side of the plant. Dwarf plants have branches that are tightly packed decreasing air circulation. The plants can stay too wet.

To maximize the longevity of these cool climate plants, we must give them special attention.
  • Plant Colorado blue spruce high. Build a small mound to provide soil water drainage.
  • Water the tree in times of drought.
  • We also need to mulch the trees lightly to keep the roots cool.
  • We should keep other plants away from them because blue spruce does not like shade or low air flow. Provide an open area for these to grow.
  • We need to fertilize spruce regularly at three times per year. Lime according to a soil test.
  • We need to spray these trees with copper based fungicides to prevent needle cast disease.
  • Scout the trees for spider mites and treat if necessary.

The bottom line is that most high altitude conifers such as Colorado blue spruce, dwarf spruce, and others do not last very long in the southern landscape without a lot of help. Even with help, Colorado blue spruce often eventually dies.