No matter how fastidious you are with your plants, there will be a residue of pests and/or diseases in your pots at the end of the season. Many of these come equipped with protective mechanisms that allow them to survive the winter and rise to infect your plants next year. Cleaning everything ready to make a fresh start in spring is time-consuming, but worth the effort.
Large container, Disinfectant/Sterilant, Waterproof gloves
Use a stiff-bristled brush to get rid of all the loose compost and debris.
Add a measure of disinfectant or sterilant to a large container of clean water.
Submerge the pot in the water and leave to soak for several hours.
Smaller pots can be done as a batch. When you take the pots out of the water, turn them upside down and leave to drain and dry. Then you can pack them away under cover until you need them.
Growing a Lily in a Container