JoAnn Haas, age 8, of Montoursville, Pennsylvania, for her question:

Why don't evergreens change color in the fall?

Trees do not change their colors in the fall unless they have to. And Mother Nature lets the evergreens wear the same color all through the year. But the oaks and maples and many other trees have thin, delicate leaves. Their fragile leaves cannot stand the frost. So the trees must shed them before winter comes. As the dying leaves become dry and withered, their green color fades. For a while, they change to lovely rainbow colors    and then they fall to the ground.

Our handsome evergreen trees have much sturdier leaves, like the tough needles that grow on the boughs of a Christmas tree. Such leaves have thick skins to keep out the cold. They also have a coating of waterproof wax. Jack Frost cannot freeze them. Piles of snow slide right off their boughs. So these trees can stay green all winter. But even on evergreens, needles do get old, dry up and fall. They are constantly being replaced by new needles.