Posted by: tysonrc | October 18, 2010

the oaks are phoning it in this year!

I have been overhearing much discussion about the leaves and their remarkable color changing abilities.  Even though it is a little late, i decided to explain what makes these colors happen and why each fall is so variable.

The leaves have three color ingredients,  chlorophyll (green), carotenoids (orange, yellow)and anthocyanins(reds, purple).  We all know that chlorophyll makes the leaves green and many think that as the green degrades, it shows the colors that were underneath it all along.  This is only partly true, and only for the carotenoids.  If you pay close attention every year, the yellows and oranges are actually pretty similar in amount and intensity.  This is because the carotenoids are there most of the season, beneath the chlorophyll, and their levels don’t change drastically.  This is not the case for the anthocyanins.  The reds and purples are the result of sugars getting trapped in the leaf.  Very sunny days and crisp nights lead to the sugars getting trapped in the leaf surface; the temperature falls too quickly after the sun goes down for the freshly created sugars to move out of the leaf.  This october has been as sunny as they come, and because of this the sassafras, dogwoods and virginia creeper are the prettiest in recent memory. 

It has also been very dry recently and this will lead to a short color season as the leaves don’t have all the energy required to create all the sugars and end up just falling off.  It is fairly uncommon for everything to come together, moisture, daytime/nighttime temps, for the prolonged period to create outstanding fall color.  On top of all that, memories of fall color are usually much more vibrant ,like many memories, and so each fall the trees are rated against a nearly impossible reference.  Luckily, here is Missouri, we have many tree species and every year a few of those species put out a fantastic show.  The best looking trees at Tyson Research Center this year are the dogwoods, sassafras and hickories, who knows what next season will bring.

–Travis Mohrman

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