The next time you have green onions, don't throw away the white ends. Simply submerge the roots in a glass of water and place in a sunny window. Periodically empty out the water, rinse the roots off and give them fresh water.
Your dishwasher is designed to clean your dishes, but with time you also need to clean this often used appliance itself. That's no surprise really. Your dishwasher is a warm wet environment that gets dirty.