Gale Petrovic, age 11, of Philadelphia, Pennsylvania, for her question:

Why does grass turn brown in the fall?

All summer long, thousands of worthy teenagers mowed the family lawn    every week without fail. Those who forgot or neglected the job learned why this chore must be done each week through the grass growing season. The sprouting grass grows in notches. The greenery is at the top of the leafy blades, the notches near the ground are brown. If we fail to mow the top notches every single week, the dead layers below refuse to sprout any more greenery and the lawn stays brown all summer.

In nature, everything changes on schedule. The grasses of our lawns and meadows have their growing season during the spring and summer. In fall and winter nature allows them a slumbering season. Then they shut down operations above the ground and their roots rest under the snows and winter rains. The summer's lovely green lawns turn brown. But do not despair, the dozing roots will sprout fresh green blades in time to welcome the spring. And if we mow every week, the lawn grasses will sprout new green carpets to keep us on the job all summer long.