Tree of Disappointment: Colorado Blue Spruce

In pots or balled and burlapped in an Iowa nursery, Colorado blue spruce is an exquisite color. Depending upon the lighting and the variety, you might describe it as silvery blue or bluish-silver. It is the official state tree of Colorado and its native distribution is limited to the dry mountains of the western US.
The native distribution of Colorado blue spruce (dark gray), copied from Gary Hightshoe’s encyclopedic, “Native Trees, Shrubs, and Vines for Urban and Rural America."
But if you go to Colorado and roam the mountains expecting to see whole hillsides aglow with glaucous blue trees, you will be disappointed. Most of the Colorado spruce are grayish-green to slightly bluish-green and have a slender, spikey snow-shedding shape. From a short distance they look the same as the more abundant Engelmann spruce and lodgepole pines. So where do the blue-silver trees come from? If you are in the mountains in spring and look closely at blue spruce, you will notice that the new growth for the year starts out with a blue-green or blue-silver color, which usually becomes mostly green into summer. But here and there a few specimens do keep their youthful blue-tinted color. These are the trees sought out and propagated by the landscaping industry over the decades selecting for the bluest of the blue.

Here in southeastern Iowa, the success of the blue spruce depends upon your expectations. For their first two decades, the trees keep their color well and form the snow-shedding dense pyramid you expect of a western mountain tree. It is a good wildlife tree — mourning doves like to nest inside the outer canopy — and the lower skirt of branches spreads out on the ground and provides year-round cover for rabbits and quail. If you are into dramatic and bold landscaping, this species will help you get there — for a while.

But after about two decades a little flaw begins to appear. Some sort of blight causes the older inner needles to fall prematurely and you begin noticing little gaps in the canopy.

Locally, when I’ve noticed that a failing Colorado blue spruce has been cut down, I’ll stop and count the growth rings. I don’t remember counting more than about thirty. In the wild dry western mountains, this species can grow a hundred feet tall and live for hundreds of years. But if that’s your expectation here in humid southeastern Iowa, you will be disappointed.

The evidence indicates that summer humidity and stagnant air is behind the early failure of the species. If grown where one side is close to another tree or tall bushes or a building, that is where the blight will begin. If grown more in the open, with good access to sunshine and breezes, the blight begins on the north side and then slowly spreads to the rest of the tree. The top, exposed to the best breezes and the most sun, often remains in good condition, while the rest of the tree below is slowly failing. There are a few large specimen around here which are growing in very open breezy spaces, but I do not know their age.

So I suggest that you adjust your expectations if Colorado blue spruce is part of your landscaping plans, and avoid disappointment later.

Note the inner bare branches beginning to show on this Colorado blue spruce.
About five years after the first canopy gaps become noticeable, the middle part of the tree begins to look thin and sparse, like this one.
A Colorado blue spruce at about age thirty. Beyond this age, the tree becomes so sparse that its landscaping value becomes negligible and people cut it down.

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