Why Leaves Fall

Most people think leaf loss follows from colder weather. Yet really, it's more a matter of light, which gets scarce and less intense as long summer days shorten into crisp fall quickies. Even in warmer climes, deciduous trees tend to lose their leaves as the summer sun gives way to the harvest moon.

For the trees, the reason is simple: less sunlight means less photosynthesis, less photosynthesis means less sugary-sweet food, and less sugary-sweet food means the party's over--it's time to shed the costly costume (those energy-sapping leaves) and sleep till spring.

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