Orchid plants need repotting for one or a combination of two main factors: Potting mix breaks down, often evidenced by dead roots, or the plant outgrowing the container. In the first case, a larger pot may not be required, simply replace the growing medium. In the second case, the plant may need dividing or may be shifted into a larger pot. Fresh media should always be used. A good general rule of thumb is to pot for the bottom of the plant, the root system, and not for the top, the foliage.