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MY ADVICE: DON'T PLANT COLORADO BLUE SPRUCE
When my wife and I built a home five years ago, one of the first landscaping decisions I made was to plant six Colorado blue spruce in the front yard. They've become nice-looking trees and are now over 10 ft. tall. However, I wish I had never planted them.
Trees should be planted with a vision of how they will look 15 or 20 years from now. The problem with Colorado blue spruce is that they are vulnerable to a whole host of problems and will eventually begin to slide downhill due to environmental stress, insect damage and disease.
Colorado blue spruce have problems in this part of Minnesota because they are not native to the humid environment we experience in spring and summer. They prefer the more arid climate of the western mountain states.
I know criticizing this beloved evergreen species is a little like denigrating apple pie or the American flag. More Colorado blue spruce get planted in our landscapes, it seems, than any other tree. It's also the tree that generates a large number of problem phone calls.
The most serious problem of Colorado blue spruce is die back that starts near the bottom and center of the tree and works its way up until eventually the entire tree becomes disfigured. This condition is most often caused by Cytospora canker, a fungal disease that spreads during wet weather. Mike Zins, University of Minnesota extension horticulturist, refers to these disfigured trees "Minnesota palm trees," because many people prune away the lower dead branches and leave the surviving green, healthy branches at the top.
Another common blue spruce fungal disease is Rhizosphaera needlecast, which can cause a tree to shed its needles on the inner portions of the lower branches.
If you were to look closely at my six vigorous blue spruce, you would see that Cytospora canker, and maybe some Rhizosphaera needlecast, have begun to infect the lower branches. These diseases will most likely worsen in the years ahead.
Carefully timed applications of a fungicide this time of year can prevent Rhizosphaera needlecast from infecting new growth. Chemical control is not an alternative, unfortunately, for Cytospora canker.
"Colorado blue spruce look so cute in the nursery - especially the blue forms when they're young - that many people can't resist planting them," explains Zins. "We need to get the word out that there are alternatives for people who like evergreens but want them to remain green and healthy for more than 10 or 15 years.
Here are some evergreen alternatives that Zins recommends (comments in quotes are from Manual of Woody Landscape Plants by Michael A. Dirr):
White Fir (Abies concolor) -White fir like warm, dry and sunny growing conditions. "Because of its growth habit and softer effect, it could well replace the spruces in the landscape; beautiful foliage, especially those trees with bluish needles."
Serbian Spruce (Picea omorika) - Can grow to 100 ft. "Öa tree with a remarkably slender trunk and short ascending or drooping branches forming a very narrow, pyramidal head; one of the most graceful and beautiful spruces."
Norway Spruce (Picea abies) - Excellent resistance to disease but grows very large, so don't plant it where a very tall and wide evergreen tree would be a problem 25 years from now.
Black Hills Spruce (Picea glauca densata) - Somewhat more resistant to fungal diseases than Colorado blue spruce. Grows slowly to 40 ft. tall.
Techny Arborvitae (Thuja occidentalis) - Also called white cedar. Severe winters can cause die-back and browning of arborvitaes, but Techny is one of the best-performing types. Grows to 15 ft. Of the cultivar 'Mission,' Dirr says "Excellent dark green foliage year-round, good hedge plant; probably the best form for northern gardens, extremely popular."
The longer I garden and the longer I answer questions from frustrated gardeners, the more I realize that no plant or garden is immune to disease and other problems.
My advice is to ask lots of questions about a tree or shrub before you buy it for your yard. What is its growth habit? How resistant is it to disease? What will it look like in 20 or 30 years?
When you purchase trees or shrubs, consider native species first, since they've survived in our local environment for centuries. Also look for disease-resistant and improved varieties.
And finally, "don't put all your eggs in one basket," horticulturally speaking. Don't plant your entire space to one species. Think rather in terms of a collection of plants. Create a "mini arboretum" in your yard. Then you won't feel so disheartened when one or two plants checks out for the great garden in the sky.
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PUTTING DOWN ROOTS:
A Delightful Blend of
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