Tuesday, September 20, 2016

Why Leaves Change Colors and the Autumnal Equinox by Carol King

Photo by Carol King
The Autumnal Equinox in Denver is Thursday, September 22, 2016 at 8:21 a.m. MDT.  So just what is the equinox? There are two equinoxes every year (September and March) when the sun shines directly on the equator and the length of day and night is nearly equal. It occurs the moment the Sun crosses the celestial equator – the imaginary line in the sky above the Earth’s equator – from north to south. This happens either on September 22, 23, or 24 every year. 

Days are becoming “shorter”and the leaves are  “changing colors”.    According to Plantalk Colorado in actuality, leaves don’t change color, they just quit producing chlorophyll, the substance that makes them green.

This happens for a variety of reasons: shorter days, falling temperatures, available water.  These are all signals to the plant to go into energy saving mode and quit producing chlorophyll:  winter is coming!

When chlorophyll breaks down, what’s left is the color that was already there:  Yellow/ carotenoids, and red /anthocyanin. These pigments are masked by chlorophyll but help protect the leaves from sunlight. After the equinox shorter and shorter days become the norm. The chlorophyll will totally disappear leaving us with beautiful colors for a short while and then dead leaves to deal with!

As you watch the leaves slowly change color and fall from the trees, you know the equinox is partly to blame.

Happy Autumnal Equinox and happy leaf peeping!