Planting trees in containers allows you to landscape over hard surfaces, like cement. Trees can provide shade and beauty to your landscape and can grace the interior of your home. Consider the tree's potential growth (when there is no desire to keep the tree pruned), the amount of space available and your winter climate when choosing a container for planting trees.
Planters located outside in full sun will dry out fast. Choose container materials that will help to retain moisture, like stone, concrete, synthetic resin or wood. Synthetic resin is a good choice for indoor use. The resin product can mimic designs that you might see cast in stone or even clay pots, yet it is unbreakable.
If living in an area where outdoor winter temperatures are continuously below freezing, choose a container at least three times the width and height of the rootball to give the tree years of cold weather protection through increased soil. Another option is to insulate the container, which may be achieved through the use of a Styrofoam lining. For only occasional nights of freezing, the container can be on a roller platform, making it easier to roll the tree into a protected area, like a garage or in a wind-blocked location close to taller in-ground trees or the house.
Trees that have the potential of growing tall, like a Redbud that can reach 20 feet in height if not pruned, are best planted in tall, wood-framed or concrete containers. The width of the container needs to accommodate a root system to balance the future canopy of the tree.
Small trees, like petite and dwarf varieties, can live in a container two times the width and about twice as tall as the rootball. In warmer winter climates (beneath USDA zone 7), clay or ceramic containers can be used outdoors. In all areas, plastic, stone, concrete, or resin containers are acceptable for planting small trees, indoors or out.
If you live in an area with minimal rainfall or if the container will be under a covered patio or even indoors, you can use a container with a built-in reservoir. The container will allow water you give the tree to seep through the dirt and then collect in the bottom of the container where it can be wicked up as needed.