As a general rule, Cymbidiums should be repotted every two to three years unless they are in semi-hydroponic culture or some media that does not break down. In that case they should be repotted when the plant becomes too big for its container. If you are a superb grower, you will have large plants with multiple leads and many leaves. These plants should be put into larger containers, or divided into several smaller pieces. Dividing Cymbidiums is a major operation and some big plants require pruning shears to cut them up. You also should be aware that when you divide a plant it may be a couple of years before they will bloom again – but the blooms will be spectacular!
Enthusiasts use special pots that are one and a half times deeper than they are wide to encourage good roots on the plants, so rather than a standard orchid pot see if you can find one that is deeper than normal. These plants get big and heavy so the taller, larger pots will help provide stability as well as give the plant the proper environment to grow.
Cymbidiums form dense clumps of pseudobulbs as they grow and will have many leafless bulbs in the middle of their pots when they’re ready to be repotted. Wait for the plant to finish flowering in the spring. This will generally occur anywhere from April to June in most plants. Remove the plant from its container and wash off all the roots being sure to eliminate any media attached to them. Hold the plant and roots up to the new container and determine what length will be about three-quarters into the new pot and then clip all the roots that will be going in the pot to encourage new growth.
This class of orchids requires moisture retentive but quick draining soil as they are naturally terrestrial. A mix of bark and charcoal mixed half and half with a terrestrial orchid mix will provide what they need to be happy.
Any medium you use for repotting your orchids should be soaked for approximately 24 hours prior to use. It needs to have enough time to absorb water so that the newly planted roots are not desiccated. Prepare the pot with drainage material at the bottom of the pot, and place a portion of medium over it at the bottom. Place your plant into the new pot and then carefully pour the medium around the roots. Tamp down carefully with your fingers, or a bamboo stake. I like to put bamboo stakes or shish kabob skewers on two or three sides of a plant to hold it in place until the plant has taken hold and becomes established in the pot.
Put the plant in a warmer and lower light position than it had been growing in before to encourage it to grow new roots and then move to its normal position in about a month.