The Colors of Fall SEASON OF CHANGE

Yak's Corner

Just For Kids

September 14, 1998

Nature leaves Yak tracks everywhere.

Look up! There's a show going on right in your own back yard. It's the fall leaf color change, coming soon to a tree near you.

Bright red, gold and orange leaves usually peak in the northeastern and midwestern parts of the United States in October.

Even earlier, though, there are changes going on inside leaves. Changes depend on two things: the shorter days and cooler nights that come every fall. Leaves contain several colors, or pigments. During spring and summer, the green pigment called chlorophyll (say "CHLOR-o-fill") is in such a big supply, it masks the other colors. Even though yellows and oranges are there, we can't see them. There is just too much green.

Leaves make chlorophyll in daylight, and spring and summer bring plenty of light. But into September and October, the amount of intense light begins to drop, and days are shorter. Chlorophyll breaks down in the dark, so eventually the leaves run out of green color and the yellows and oranges can show through.

Red leaves are a little different. Cool nights in autumn signal the tree that winter is coming, and the tree forms a protective layer between its leaves and branches.

That layer traps sugar, which the leaf keeps making on bright, sunny days. The sugar builds up inside the leaf and is turned to red pigment. That's why the brightest reds will be where trees get the most sun and can make the most sugar.

Pub Date: 9/14/98

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