Three (3) 3.0 gallon circular plastic nursery pots.
 
Blow Molded Containers are a sturdy and cost effective pot, ideal for nursery use.  We use these for our nursery stock we sell, as to not break the bank on pots.
 
Made by A.M. Leonard, NSI Blow Molded Containers are made of strong, flexible 100 high density polyethylene, offering exceptional durability, strength and value. They are approximately 11" wide x 9.5" high and hold 3.0 gallons of soil.