From my perspective as a Dendrobium orchid, timing is everything. Please attempt this procedure when I am in my active growth phase, typically in the spring just after I have finished flowering and as you notice new growths (called "pseudobulbs" or "canes") beginning to develop and fresh, white root tips emerging from my base. This is when my metabolic energy is at its peak. I will have the greatest reserves stored in my thick canes to withstand the stress of division and to fuel the rapid root and shoot development of the new divisions. Dividing me while I am dormant or in bloom redirects precious energy away from flowering and can cause severe setback or even death to the divisions.
Begin by gently removing me from my pot. You may need to carefully cut the pot away if my roots are extensively adhered to it. Soak my root mass beforehand to make the roots more pliable and less prone to snapping. With your fingers, patiently untangle the root ball, removing old, decomposed potting medium. My structure is sympodial, meaning I grow from a horizontal stem called a rhizome. You will see several raised, leafy canes connected by this rhizome. Using a sterilized and sharp knife or pruning shears, cut through the rhizome between pseudobulbs, ensuring each new division has at least three to four healthy, mature canes and at least one new growth (or "lead"). This is crucial; a division with fewer canes lacks the stored energy and food reserves to support itself until its new root system becomes fully functional.
Once divided, select a new pot that is only slightly larger than the root mass of the division. I am an epiphyte; in nature, I grow on trees with my roots exposed to air. Therefore, I require a very fast-draining and aerated medium. A mix of coarse fir bark, perlite, and horticultural charcoal is ideal. Do not use soil, as it will suffocate and rot my roots. Position the division in the center of the pot, spreading the roots out. Hold it at the desired height—the base of the newest pseudobulb should be just at the top of the medium—and then fill in around the roots with the fresh potting mix, gently tapping the pot to settle it. Avoid burying my rhizome or the base of my canes too deeply.
This is the most vulnerable time for my divisions. Do not water me immediately after repotting. Instead, place me in a warm, shaded, and humid location for about one to two weeks. This allows any root wounds to callus over, preventing fungal or bacterial rot. After this period, you can begin light watering, gradually returning to your normal watering routine as new root growth becomes evident. Hold off on fertilizing for at least a month, as my tender new roots can be burned by salts in the fertilizer. With high humidity, bright indirect light, and careful watering, my divisions will establish themselves and soon begin a new cycle of vigorous growth, eventually rewarding you with their beautiful blooms.
