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  • Greg Graves

Changing Climate and Our Trees

We had an arborist out yesterday to take down four dead trees, three Alders and a Western Red Cedar. All were the result of several years of summer droughts. We had another larger Alder come down a week ago on its own. It was suppose to be part of this take down yesterday.

Dead Cedar

According to our arborist, he can’t keep up with the demand he gets from people wanting dead trees taken down on private property. I think the demise of these four go back to the more severe drought of 2015. In 2015 we had a very dry winter followed by our normally dry summer. That brought our normally high water table down substantially. The last couple winters have been wetter than normal but the dry season has started earlier and lasted longer. This year we had one of the wettest January, February, March and Aprils on record and since have received less than one inch of rain.

For us in a normal year we received most of our 45 to 50 inches of rain between October 1st and June 30th. July, August and September are usually very dry. These conditions are what our native plants are use to. Even though the rainfall amount is close to the same, moving the dry season a few weeks on both ends can have a dramatic effect on the native plants. This year the dry season began six to eight weeks earlier than last year. With the drier summer the plants try and adapt, some deciduous trees by shedding their leaves earlier and the conifers by dropping some of their older needles earlier. 

Drought kills a tree when it loses more water through its needles and leaves than it can replace from the soil with its roots. Without water, trees can’t make food by photosynthesis. Their interior plumbing can also fill with air bubbles, causing tissues above the damaged tissue to die. Forest-health experts predict the effects of the severe drought will be with us for some years to come, as trees continue to struggle and even die. It is typical for effects to unfold in the next season, when a tree that used up its resources to get through the previous year has nothing left to defend itself or thrive in the next season. With the stressed trees come the perfect opportunity for pests to move in creating more damage for the already weakened tree. 

Goats helping to clean trees

The city of Seattle had reported in 2016 to losing over 500 trees in the park system. In a normal year it usually around 100. Many Northwest municipalities are having the same problems. If you look as you drive around, green belts close to freeways, you’ll notice sporadic dead trees against the green hillsides.

fallen Alder

There is no simple solution to this climate change problem. We as home gardeners may want to reconsider the use of some of our native big trees in the landscape. I thought having this cedar at the edge of the property that didn’t receive any supplemental water would be a good solution but in todays conditions it isn’t. We do have older Western Red Cedars on the very back of the property but they are close to a wetland which may be a perfect site for them now. Over time who knows. Without the extended cold season everything changes.

I know researchers at the University of Washington are studying the effects of our current climate conditions at the arboretum. Hopefully these professionals will be better able to diagnose the changes on our landscapes and possible solutions.


Charlie and Cedars

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