All containers must be suitable for their purpose. They must fit the plant and they must contain sufficient compost for that plant to flourish. They must be strong enough to withstand the elements. They must also have adequate drainage to allow surplus water to drain away when the plants are watered.
Drainage. Almost all garden containers that you can purchase will have proper drainage holes already in place but if they don’t you will have to make holes in the bottom. The same goes if you have made the containers yourself. Make sure that there are enough drainage holes and if you are lining the container with polythene see that there are holes in the polythene that align with the holes in the bottom of the container.