Flower pots provide an ideal environment for mildew growth. These pots are usually warm and kept damp, with little airflow to stymie fungus growth. Mildew growth usually shows up in pots as white or black growths on the inside rims or around the bottom, near the drainage tray. You should clean these pots periodically. Doing so will keep mildew from spreading and will keep your plant pots looking much nicer. Cleaning won't take much time, and you probably already have most of the supplies you will need.
Remove flowers or plants from flower pots to be cleaned. Mildew will likely be present not only around the visible edges, but down throughout the pot.
Fill a sink or large bucket with warm soapy water. Dish soap or hand soap is fine for this step.
Place pots in the soapy water and scrub with a sponge. This removes much of the surface dirt and mildew. Rinse each pot with warm water and set to the side on dry towels.
Drain the soapy water from the sink or bucket and refill with a vinegar and water solution. This solution should be one part white vinegar to two parts warm or cool water.
Place flower pots in this solution for about one hour. Remove them after this time and wipe them down with a damp cloth. Place them on towels to dry.