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Extension > Yard and Garden News > Pruning Trees to Avoid "Disasters"

Friday, September 30, 2011

Pruning Trees to Avoid "Disasters"

Karl Foord, UMN Extension Educator

USDA Forest Service
Figure 1: Crown thinning

Karl Foord, UMN Extension Educator
USDA Forest Service
Figure 2: Crown raising

Tree planted in 1997.

Before

After
I have Autumn Blaze maple trees that produce great fall color and grow very quickly. In the tree trade they are known as "disasters" because they produce a very dense canopy that is subject to limb breakage in ice storms and uprooting in high winds. To avoid my trees becoming disasters I have pruned them to the point where I was pretty high up in the tree and getting in precarious positions. It was time to get an arborist. I took pictures of the trees before pruning and after pruning to see the difference and then looked on line for verification.

The arborist pursued two strategies, crown thinning (Figure 1) and crown raising (Figure 2) both taken from the USDA Forest Service publication, "How to Prune Trees".
The before and after pictures show that some lower limbs were removed and how the center of the tree was opened up, reducing wind resistance and the number of limbs available for ice accumulation.
The trees in the picture were planted in 2000. I have another set of Autumn Blaze maples planting in 1997. What is the value of the trees? If they are damaged in a storm, how much time has been lost? I would rather hedge my bets and see that they are properly pruned. The last photo shows one of the trees planted in 1997.

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