Most plants should be repotted when their roots become pot-bound. A potbound plant can be recognized easily because the soil dries out quickly, and the roots often grow through the drainage hole. Repotting is best done when the plant is in active growth. Generally, a new plant does not need repotting unless it is purchased in a temporary container. Otherwise it is usually best not to repot a new plant until it has begun to adjust to its new environment.
Before it is repotted, the plant should be watered so that the soil will be neither muddy nor crumbly, The new pot should be only one size larger than the old pot. A piece of broken pot (shard) should be placed over the drainage hole - of the new pot and a cushion of soil in the bottom of the pot. To remove the old pot, the plant is turned upside down. The edge of the pot is then tapped sharply against a table, bench or shelf with one hand to dislodge the root system, which is caught with the other hand held underneath the pot. The root system then is placed in the new pot, and more soil is filled in around the roots. The base of the pot is rapped against the table to settle the soil, and the repotted plant is then watered.
The basic potting mixture consists of one part topsoil, one part humus or peat moss, and one part sand or perlite. Jungle plants prefer a richer mixture, or a greater proportion of humus, and succulents prefer a sandier mixture. With ready-mixed, sterilized, and packaged soil so readily available, few indoor gardeners mix their own soil. There even are package mixtures designed especially for undrained planters. These contain enough charcoal, sponge-rock, and other materials to provide a kind of built-in drainage. Such a planting mixture is ideal for hanging baskets because of its light weight.