The diameter of the container has no bearing on drainage. Similar drainage patterns occur regardless of diameter in pots with the same depth. Therefore, there are no advantages to using excessively wide pots. Most growers prefer pots that are deeper than they are wide. Volume Size of nursery stock will dictate the necessary volume of containers.
Large plants require equally large containers to prevent stunting of root and shoot growth.
This can be difficult for inexperienced growers to judge. Refer to the American Standards for Nursery Stock to obtain the latest container size requirements for a specific nursery stock size. Growers often group together plants in like size containers for more accurate irrigation and easier handling and maintenance. The cheapest pots, and easiest to stack, are those which are round in horizontal cross section. Most growers select this type for the advantages given above, even though their use remains somewhat controversial.