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IPR News Radio's Sunday host, Cheryl Bartz, tells us what to look for as we wander around northern Michigan, helping us notice the little wonders all around us.

Red October

Sunny days cause fall foliage to show more red pigments along with the oranges and yellows. (Photo: Cheryl Bartz)
Sunny days cause fall foliage to show more red pigments along with the oranges and yellows. (Photo: Cheryl Bartz)

This week promises to be peak color for most of our listening area. There are quite a few sunny days in the forecast, which could mean a lot of red in the mix.

You may recall from elementary school science classes that yellow, orange and red pigments are present in leaves throughout spring and summer, but they only become visible when the tree stops making green chlorophyll in the fall.

You may have learned that, but….Hold on! That story is not completely true.

As days become shorter, deciduous trees prepare to ditch their leaves because there won’t be enough sunlight during the winter for them to carry out photosynthesis. The leaves begin to dismantle the chlorophyll and transport the components down to the roots.

That does indeed leave the yellow and orange pigments visible, just as your science teacher taught you. But science has marched on and there is now consensus that the red pigment is actually made by leaves in the fall.

However, there is still debate about why some leaves turn red.

The strongest argument seems to be that the red pigment functions as a sunscreen to keep leaves viable longer. That gives the trees more time to transport valuable nutrients back down to the roots.

An alternative hypothesis is that red color discourages insects from laying their eggs on those leaves.

It’s a good lesson about how science works. Just because something seems like established truth, scientists don’t stop digging to learn more.

And sometimes we just need to accept that what we once believed was true is not, and revise our picture of the world accordingly.

If you’d like to know more about leaf color change, check out these links. Warning: this is a very deep rabbit hole.

Cheryl Bartz hosts IPR's Sunday programming and writes a (mostly) weekly essay called "What's Up Outside?"