Why you should not plant Colorado blue spruce tree

By Bev Johnson | The Daily Journal

Published Saturday, November 15, 2008

This is the time of year that spruce trees normally drop some needles from the inside of the tree. But this year, the tree clinic at the University of Minnesota has gotten many samples of Colorado Blues with all kinds of diseases.

This tree is not native to Minnesota. It grows fast, lives hard, and dies young — at the ripe old age of 30 or so.

We have seen many spruce cultivars with rhizopheaera, a fungal disease that infects this year’s needles. The needles turn purple to brown and fall from the tree leaving the inside of the tree naked.

As the disease progresses, the infected branches die leaving you with a very ugly tree. Only the outer branches are green. This disease starts at the bottom of the tree where humidity levels are highest then spreads up.

It usually starts on one side of the tree. It will eventually kill the tree although it may take a long time to die.

Time for you to plant a replacement before the original dies or you can’t stand to look at the ugly thing any longer.

Wisconsin plant pathologists have reported a mystery disease of blue spruce. The symptoms are needle drop, yellowing of needles and shoot blight. They thought they had identified the fungus as Dothiora, but the USDA says it’s not.

Here in Minnesota, two nasties that affect our blue and white spruces in a similar manner have been identified as Leptosphaeris and Sirococcus. The latter, only causes severe problems during extremely wet springs like the one we had this year.

The University says the disease “exploded” this spring, disappeared in the summer then popped back in September on stressed blue spruce.

One symptom is a twisting of the needles. It looks like herbicide damage.

So, what should you do to minimize future problems? First of all, don’t plant Colorado Blues. Plant a native white or Norway spruce instead.

Then, keep your trees well watered, especially in the fall. Mulch it in the fall, and if you see some symptoms in the spring, get your tree sprayed with a fungicide.

It needs to be done when the candles are about a half inch long and then again in about two weeks. The Extension office has the name and phone number of a fellow who does this spraying.

Another tree not to plant is any ash. The experts say any ash is “toast” — a real scientific term.

It may not happen next year, but, so far, there is no treatment to stop the ash borer.

The Emerald Ash Borer is not in Minnesota yet, but when it does get here, it will kill your ash tree.

The only good thing about this is ash trees are good firewood. They split easily and burn hot.

A nice side effect with the price of heating oil and gas so high.

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Bev Johnson is a master gardener for West Otter Tail County.