Halloween orange

It seems appropriate to feature the “orange-y” colors of autumn as we celebrate All Hallow’s Eve today in recognition of saints, martyrs, and our own dearly departed.

orange sugar maple leaves

Some maples and oaks turn a brilliant orange in the fall as the chlorophyll in their leaves breaks down and the underlying carotene pigments in the leaves are exposed.

fall color in a birch-maple forest

The birches and maples glow in afternoon sunlight with shades of yellow and orange.  

Yellow leaf colors derive from the unmasked xanthophyll pigments in the leaves; orange colors are a result of underlying carotene pigments.  These pigments are always present in the leaf, helping soak up the excess light energy that impinges on a leaf in bright sunlight and passing some of that energy on to the chlorophyll molecule for photosynthesis.  But photosynthesis shuts down in the fall, with low air temperatures and short daylength, and chlorophyll stops being synthesized. Then, xanthophyll and carotene pigments absorb light in the blue, blue-green, green, and long red wavelengths, leaving the yellow and orange colors to be reflected to our eyes, and producing the kaleidoscopic show we call fall color.

red oak leaves

Even this red oak is tending toward more orange than red at this time of the fall.

wm o'brien-state-park-fall color

The prairie glows in orange colors in the fall, accented by yellow and orange leaves of the oak, maple, and birch tree border.


With all the natural orange color of fall around us, it’s no wonder pumpkins have become the symbol for Halloween celebration.  (Photo credit:  Gary Halvorson, Oregon State Archives [Attribution], via Wikimedia Commons)

pumpkins and ghost

A Halloween ghost seems to be admiring the pumpkins carved by the grandkids.  

Happy Halloween to all!

One thought on “Halloween orange

  1. Pingback: Why are some leaves red? | Back Yard Biology

Please Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s