Also, determine how much time and money is available for container and planter maintenance and select accordingly. With regard to container or planter size, a confined tree root system ideally should have two cubic feet of substrate for every square foot of tree canopy. Consider the mature size of the desired tree and design or select containers or planters with adequate root volume. Remember that the greater the substrate volume in the container or planter, the greater the temperature buffering, and the reserve of water and nutrients. In exposed and windy areas it may be desirable to line containers and planters with supplemental insulation.
Drainage is very important when designing or selecting containers and planters.
For containers, and planters with constructed bottoms, be sure that channels exist to drain away excess water. Planters that are open to the ground should be built atop soil through which water readily drains. If containers must be used to permit seasonal relocation to more temperate conditions during winter months, select small containers and trees. To avoid container damage or structural collapse if containers are used on above ground patios, rooftops, etc., keep the total weight of the container, substrate, trees and water in mind. Even with careful container and tree selection, trees may outgrow the volume of their containers.