Trees Please Hamilton

Green Solutions to Air Pollution

TREE TUESDAY: Blue Spruce Mystery

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Last week’s blog post sang the praises of citizen science, and today we have a story to back it up. 

We were walking down by Beach Road in Crown Point and came across a startlingly blue, Blue Spruce. One of our Trees Please staff commented that she had never seen a Blue Spruce this vibrant before. Here’s a picture:

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Close up of the Blue Spruce’s needles

So, with our curiosity piqued, we started asking questions. Why is this tree more blue than others? Could it be due to air pollution from the neighbouring industrial area? This is where question based learning kicked in. 

After some research, we learned that the blue colour comes from epicuticular waxes on needles that reflect specific light wavelengths. The more wax there is, the more blue the needles appear to be. So why might the wax on this tree’s needles be thicker than other spruces we’ve encountered?

The wax thickness is genetically determined, but can also be influenced by habitat. Several studies have shown that spruces with the bluest needles have been found at high elevations and with winter exposure. Does this mean that there is a correlation between hardiness and blue colour? Does air pollution impact the wax thickness?

Turns out that air pollutants such as Nitrogen Oxides, Sulfur Dioxide, particulate carbon, and other hydrocarbons, actually degrade the wax thickness. Our original hypothesis that pollution from nearby industry had made the tree more blue was likely false, since thinner wax produces less of a blue colour. 

Although we were incorrect, the process of question based learning was a satisfying learning experience. Participating in this citizen science project got our brains jogging about something that might have passed by unquestioned otherwise!

 

Source:

https://www.lawyernursery.com/PDF_static/articles/2010_Jan_What_Makes_My_Blue_Spruce_Blue.pdf

 

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Author: treespleasehamilton

A project of the Hamilton Naturalists' Club and Environment Hamilton. Funding by Ontario Trillium Foundation.

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