Orchid splitting, or division, is a common horticultural practice involving the physical separation of a single large orchid into multiple smaller, genetically identical plants. Division prevents the overcrowding of pseudobulbs and roots, which can lead to the deterioration of the potting medium and the eventual decline of the orchid. By dividing the plant, growers renew its environment and stimulate new growth points.
Identifying the Need and Timing
Several signs indicate an orchid is ready for division. The plant is often “pot-bound,” where the root mass is dense and tightly fills the container. New growths may extend over the container’s edge, making it difficult for the plant to anchor itself or establish new roots. The potting medium also breaks down over two to three years, losing its airy structure and retaining too much moisture, which leads to root problems.
The optimal time to divide most orchids is immediately after the active blooming cycle has finished. This period coincides with the beginning of a new growth phase when the orchid is actively producing new roots and pseudobulbs. Dividing then allows the new sections to establish quickly and minimizes stress. Attempting division while the orchid is in full bloom or when new flower spikes are forming can cause the plant to abort buds or experience stunted growth.
Preparing Tools and the Plant
Preparation for division requires a sterile procedure to protect the orchid from pathogens. A sharp cutting instrument, such as a razor blade, knife, or shears, is needed for clean cuts. Sterilization is accomplished by wiping the blade with 70% isopropyl alcohol or briefly heating the metal parts with a flame. This step must be performed between cuts, especially when dealing with different plants, to prevent the spread of viruses or bacteria.
Before cutting, unpot the orchid and remove the old growing medium completely from the root system. Gently loosen the roots and rinse them under lukewarm water to expose the rhizome and view the plant’s structure. A powdered fungicide, such as commercial orchid fungicide or common household cinnamon, is needed to treat fresh wounds. Cinnamon acts as a natural desiccant and mild antifungal agent, helping cut surfaces dry and seal quickly.
Dividing Based on Orchid Type
The method for splitting an orchid depends on its growth habit: sympodial or monopodial. Sympodial orchids, such as Cattleya, Cymbidium, and Oncidium, grow horizontally along a rhizome, producing new growths and swollen pseudobulbs sequentially. To divide these types, the rhizome is cut into sections. Each division should retain a minimum of three to five mature pseudobulbs, ensuring the new plant has sufficient stored energy to support root growth and flowering.
Monopodial orchids, including Phalaenopsis and Vanda, grow vertically from a single, upright stem and do not form pseudobulbs. Division of the root mass is not recommended for these orchids. Propagation for monopodial types is typically done by separating plantlets called keikis, which are clones developing naturally on the flower spike or stem. A keiki is ready for separation when it has developed at least three leaves and several roots that are two to three inches long.
Post-Division Repotting and Recovery
After division, each new section must be potted into a container appropriately sized for its reduced root mass. Selecting a pot that is too large can hold excess moisture, leading to root decay. The new potting medium should be fresh, well-draining, and formulated for the specific orchid type, such as fir bark mix or sphagnum moss. When repotting a sympodial division, place the oldest portion of the rhizome against the edge of the pot, allowing maximum space for the future growth of the newest lead.
Immediate withholding of water for several days to a week is essential post-division care. This delay allows the freshly cut and treated roots and rhizome surfaces to fully callous over and seal. Callousing prevents the entry of waterborne pathogens that cause rot. The newly potted divisions should be placed in an area that provides bright, indirect light, avoiding harsh direct sun exposure. Maintaining moderate to high humidity and stable temperatures encourages the development of new roots.