Guest Author - Susan Taylor
As a general rule, Dendribums 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. If you are like most growers, you will have a plant with many leafless green stalks and the canes with leaves will be growing out of your pot.
Dendrobiums are sympodial orchids, orchids that grow sideways along a stem that looks like a rhizome. Roots will grow out of the stem as the cane-like pseudobulb forms and grows upward. If you have leafless canes, cut these back and try using them to grow new divisions. Some types of Dendrobiums can be forced to grow many new plants by placing a cane horizontally and allowing it to start new plants. They also will easily make new keikis (new baby plants) all along their canes. These can be cut off and planted when the roots are about 2 inches or 5 centimeters long.
Wait for the plant to finish flowering and start new root growth. 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. Dendrobiums need to be under potted – they will not flower well if you put them in a pot that is too large. I like to put black lava rock in the bottom of the pot to give it extra weight to hold the plant since most Dendrobiums are tall and therefore top heavy.
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.