In order to encourage exceptional growth and flowering, orchids should be repotted annually. While the same pot can be used, it is recommended to use a slightly larger pot to encourage new root and plant growth. If rotating pots among orchids in various developmental stages, it is important to properly sterilize the orchid pot before repotting to prevent the spread of disease, mold and fungus.
Remove the old plants from the pots and dispose of all the old potting soil.
Wash the pot with soap and water to further remove any soil and hard-water buildup from the pot.
Sterilize the pot by soaking it in a mixture of one-part bleach and nine-parts water for at least 3 hours. This will kill any diseases, bacteria or fungus that may have developed in the pot from its prior use. Remove the pot from the soak. If the pot is plastic, rinse under running water and dry. If the pot is made of clay, then soak the pot in clean water for at least 3 hours to remove all the bleach. If preferred, a commercial sterilizer such as "Physan 20" can be used instead of bleach.