Arborvitae trees in the landscape

July 18, 2014 by  
Filed under Wind Energy Tips

Posted: Thursday, July 17, 2014 1:43 pm
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Updated: 2:42 pm, Thu Jul 17, 2014.

Arborvitae trees in the landscape

Lance Ellis

University of Idaho Extension Educator

Teton Valley News

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One of the most planted, yet many times unsuccessful to get established and to grow trees in the landscape are arborvitae trees. They look much like a juniper, but are not junipers, and do not have the same undesirable attributes that many junipers have. Arborvitae are known for their tall columnar shape and emerald green foliage. They are sold at almost all garden centers and are easily found. Here are a few tips for selecting the right arborvitae for your yard.

The first criterion is to choose a variety that is cold hardy for your location, which under most circumstances is not an issue. Most nurseries only sell cold hardy varieties of this plant, but occasionally a cold sensitive variety may be shipped in, so check the label to make sure that it is cold hardy to at least a zone 4. Most often arborvitae are sold potted or have their root systems balled and burlapped. Balled and burlapped means that the trees were grown in a production field, and then dug, and had their root ball wrapped in burlap to prevent it from falling apart.

Too often when these trees are dug, the root system is severely damaged and reduced, and the tree cannot recover from the shock of being balled and burlapped and ends up dying after being planted. Being an evergreen tree, they are using water all year round, and for this reason, fail to survive in our windy and dry climate after losing most of their root system when they are dug and transplanted. The trick to getting your arborvitae successfully transplanted is to buy a smaller tree at planting, which because of its size, has had less root damage, and also has less top growth to try and support on a small root system.

After planting it is crucial the trees have sufficient watering or else they slowly dehydrate and die. Arborvitae are notorious for winter dieback due to dehydration. Giving these trees a deep soaking of water throughout the late fall into the early winter helps them to resist winter damage from cold drying winds. This type of evergreen should never be used as a wind break tree, as they do not handle the drying effects of the wind.

If they are in a windy location, they will have sections of the tree die out from wind desiccation, which once a branch turns brown and dies it should be pruned out. A dead branch on a tree will never come back to life, so just prune it out and allow the tree to refill itself in that spot. They generally will regrow in pruned out empty locations if there is ample sunshine reaching that spot. Most trees will regrow bare spots as long as there is sufficient light available. (It’s too bad that re-growing hair isn’t the same way.) What the tree is doing is investing in branches where it can get a return from photosynthesis. If a spot on the tree is severely shaded, it will not generally send out new branches or leaves in that area.

It’s just not worth it for the tree to waste that energy on a branch that will never produce any food for the rest of the tree. Arborvitae generally don’t have many pest problems in our area with the exception of spider mites. These insects attack several different plants. If your arborvitae begins to take on a bronze or yellowish color, especially where there are dusty conditions you may want to check for this pest by shaking a branch over a white sheet of paper. If little dots begin to move on the paper you probably have spider mites.

Fine webbing is also a sign. They are very small and can build up rapidly. They love dry and dusty conditions so if you end up with a problem you can spray the foliage with a strong jet of water to dislodge them, which will also wash off the dust. Doing this every few days for a few weeks, along with proper watering, will go a long way in reducing problems with this pest.

For questions contact Lance at 624-3102.

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Thursday, July 17, 2014 1:43 pm.

Updated: 2:42 pm.

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