GRAND RAPIDS, MI – Gardeners have noticed green, fully formed tomatoes stubbornly hanging onto their vines, refusing to progress toward the ripe, vibrant vegetables of summer eagerly awaited by many.

This is the time of year when Nicole Hughes gets constantly distracted by the fall foliage as she drives around North Carolina. "I'm always looking," says Hughes, a biologist at High Point University.

Leaves often turn brilliant colors in autumn. One of those colors has generated a lot of heated debate among scientists in recent years. Autumn is a big time for trees. Many shed their leaves, and of ...