For various reasons, many gardens include plants grown in containers. Pots and tubs are portable, so frost sensitive species which grow in full exposure from spring to autumn may be moved to sheltered locations prior to cold winter weather. Some plants which are showy in particular seasons may also be moved out of the way when not so ornamental or if hard pruning is required. Some garden enthusiasts enjoy gardening in containers just so they have the option of changing arrangement of some of the plants in the landscape as one might move furniture around inside the home.

Containers may be used to give height to low growing plant species, annual flowers or even small specimen plants. Species with specific soil requirements are often grown in containers so that they may have their own private space for their roots, where soil conditions will not be affected by the surrounding soil.

Growing plants in containers is completely different from growing the same plants in the ground. Plants are more  likely to experience problems with confined roots, drying soil, poor drainage and even increased soil temperature. In most situations, soil is only used in large containers or tubs, because it doesn’t drain well when the only outlets are drainage holes at the bottom of a pot. Potting “soil” is actually composed of various non-soil components, such as fir bark, sand, perlite or vermiculite. Not only does it drain very quickly, but it retains sufficient moisture between watering. The light weight of potting soil is also desirable if containers are to be moved.

To prevent roots from being cooked, containers should be well insulated. Black vinyl cans which are used by nurseries are not suitable for garden use because the black absorbs heat from the sun and the vinyl is so thin that the heat is transferred directly into the soil. Nursery cans may only be used if contained within larger containers or baskets. Wood pots and barrels are well insulated and stay as moist as the potting soil within them, so roots will not desiccate as they come into contact with the inner surface. Unglazed clay is probably the best material for containers. It is very well insulated and has good moisture retention. Roots which come into contact with clay can not distinguish it from rocks or other material they may encounter if they were growing in the ground. Although glazed pots are not as appealing to roots, they are well insulated and usually reflective to sunlight.

Because thorough drainage is necessary, it is important that dishes used to catch water are not allowed to hold it between watering. Standing water breeds pathogenic organism such as those which cause root rot (and mosquitoes.) What plants want most out of their containers are conditions resembling as closely as possible those they would find in the ground.