Remove any dirt by first brushing it off and then washing the pot with soap and water. Rinse the pot and let it air dry thoroughly.
Open the crack slightly with a wedge if necessary and apply a thin layer of silicone caulk throughout the entire crack. Remove the wedge.
Wrap the pot with a piece of wire to squeeze the crack together and secure the ends of the wire by wrapping them around each other. Allow the silicone to dry. The time varies depending on the manufacturer, but overnight will work well. Remove the wire and check the crack. Peel any excess silicone away.