It's one of those questions you're never prepared for. You should have been. You knew it would come and you've already dropped the ball on so many other important questions, like 'Why is the sky blue'?, 'What is wind'?, and 'Why do Grandma's teeth fall out when she laughs'?.

Now, it's autumn and your son's at that age, when he wants to know everything'right now! And here you are, driving him home from pre-school on an otherwise perfect fall day, and he hits you with it: 'Why do trees change color'?

You feel suddenly diminished, inadequate'unqualified to be the guardian of this budding intellect in your back seat. You're thinking of ways to distract him long enough to dig your moldy old biology book out of the box in the back of the garage (you knew it would come in handy, one day). You're kicking yourself for never having the answers to these questions; your son must be getting the idea, even at his tender age, that you're the dumbest parent on the planet. How is he ever going to trust you with the really important stuff?

This beautiful day has become a parental nightmare you'll remember for the rest of your life.
But guess what? You're really not as stupid as you think. You see, here it is'the twenty-first century'and even the brightest scientists don't know exactly all the processes involved in the changes in tree leaves!

Here's the nutshell version of what we know, with translation into simple enough language for your son:
The green in tree leaves is this stuff called chlorophyll. Chlorophyll and sunlight together help the trees ingest their main source of nutrition'carbon dioxide. So, sunlight and chlorophyll are kind of like our knife and fork, and they help the tree to eat the air that we breathe out'that's what makes the tree grow big and strong.

In the summertime, when the sun is out for long periods of time, the tree eats and eats until it's full. Then, in the fall, the tree gets ready for a long nap'kind of like Uncle Frank after a big meal. The tree gets rid of the green chlorophyll, and the real colors of the leaves come out, for a short time.

Then, in the spring, the tree wakes up, hungry, and makes new leaves with chlorophyll, to fill itself up, again'kind of like Uncle Frank, when he wakes up from his nap, and makes himself a big sandwich. And the chlorophyll makes the leaves stay green, until the tree is full, again, in the fall.

See? It's easy. If you have a young child, memorize it. Not only will you be able to keep a perfect fall day perfect, you'll also be the genius your son expects you to be.

Until he asks that pesky question about snow'