If you're a home gardener with a patio or roof deck and you've been eyeing that bamboo or palm tree at the garden store, then you'll likely be shopping for some extra-large planters. Landscaping with large trees and plants with above ground planters is a viable option when below ground planting is not available. But, environmental factors such as temperature extremes along with a limited volume for root growth can be challenging to overcome.
What might be the ideal sized planter for a queen palm might not be so ideal for that Japanese maple tree. In general though, dwarf or semi-dwarf trees are more suitable for container planting. Planters though, no matter how large, are not effective insulators against extreme temperatures. Both heat and cold can be magnified in an above ground container. Tree roots are more delicate than stems when it comes to cold weather and if the soil substrate surrounding the tree roots drops below freezing, the tree may dry out due to the inability of the roots to absorb water from a block of ice. Likewise, extreme heat conditions increases water evaporation in the soil and dehydration of the tree.
Terracotta planters, while aesthetically pleasing and heat resistant, may not insulate against frost as well as other materials. Plastic containers are light weight, hold moisture well, are frost resistant, but do not insulate against high temperatures. Stone and wood planters, although more expensive, offer a nice balance between aesthetic appeal and durability. Extra-large fiberglass planters are economical, lightweight and can be molded into shapes that work well with the natural design of your garden.
Shopping for an extra-large planter is a balancing act between design, economy and durability. Making the right decision will have a long term effect on the beauty and hardiness of your garden.