Why is Fall so colorful?

The leaves are turning amazing colors before piling up in your yard.  Reds, oranges, yellows, and browns.  What happened to all the green?

Bright yellow tulip poplars.

Green chlorophyll is what makes trees green.  They can absorb any color but green, so green is all you see.  However, this green-reflecting pigment is expensive to produce.  Its worth it most of the year because the sugar payoff is so high, but with the days getting shorter the trees start to cut their losses and focus on storing up sugar in more protected areas like the trunk and roots.  As the green disappears, other colors start to appear.

Yellows and oranges were always there.  They are other types of chlorophyll that help funnel light into the tree.   The green chlorophyll just got in the way before.

Reds are something different.  I just learned that the reason leaves turned red is because as the tree starts blocking off the veins that lead to the leaves, some of the sugars get trapped in the leaf.  The trapped sugar reacts to the sun and other chemicals in the leaf to turn red!  This is why extra sugary trees like Maples and Sweet Gums tend to be redder than other trees.

Browns are similar to the reds, except instead of sugar being trapped, its just extra trash molecules.  I think that since it is such a mix of random bits and pieces, its like what happens if you mix all your colors of paint together.

Lots of complex thing going on in this red maple leaf.

Next time you see colored leaves, remember how they represent how complex interactions take place in each leaf!