Orchid propagation, often described as rooting a “cutting,” is a method of asexual reproduction that creates a genetically identical clone of the parent plant. Unlike many common houseplants that root easily from a simple stem section, orchids require a specific approach tailored to their unique anatomy. Successful propagation involves separating specialized plant structures, such as backbulbs or aerial plantlets, and encouraging them to establish their own root system. The goal is to safely separate a viable piece of the parent orchid and provide the precise conditions necessary for it to mature into an independent plant.
Selecting the Proper Propagation Material
The specific material used for propagation depends entirely on the orchid’s growth habit, which falls into two main categories.
Monopodial orchids, like Phalaenopsis and Vanda, grow vertically from a single stem. Propagation material for these types is typically a keiki, a small plantlet that develops on a flower spike or the main stem. A keiki must have at least two to three healthy roots that are one to three inches long before separation to ensure survival.
Sympodial orchids, including genera like Cattleya, Dendrobium, and Oncidium, grow horizontally along a rhizome, producing thickened storage stems called pseudobulbs. Propagation relies on using “backbulbs,” which are older, leafless pseudobulbs that store water and nutrients. When dividing the rhizome, each section should contain a minimum of three to five pseudobulbs, with at least one being a live, active growth known as a “lead.” If using only backbulbs, they must be firm, healthy, and have a dormant “eye,” or node, from which new growth can emerge.
Tools and Techniques for Making the Cut
Maintaining absolute sterility of your tools is necessary to prevent the spread of viral or fungal diseases. Before making any cut, instruments such as a razor blade, sharp knife, or pruning shears must be sterilized. Methods include soaking in a 10% bleach solution, wiping with isopropyl alcohol, or briefly flaming the blade.
For sympodial orchids, cleanly sever the rhizome between the pseudobulbs, ensuring the desired number of bulbs remains attached to the division. When removing a keiki from a monopodial orchid’s flower spike, cut the spike two inches above and two inches below the base of the plantlet. This attached spike piece helps anchor the new plant in its medium. Immediately after separation, treat the fresh cut on both the parent plant and the cutting to prevent rot and infection. Dusting the wound with ground cinnamon (a natural fungicide) or applying a commercial horticultural fungicide powder are effective treatments.
Creating the Ideal Rooting Environment
The environment for the new cutting must provide high humidity while allowing for adequate air circulation to prevent fungal growth. Sphagnum moss is a popular rooting medium because it retains moisture well while remaining airy, and it is frequently used for potting keikis and backbulbs. The medium should be damp, but never saturated, as waterlogged conditions will quickly lead to rot.
A clear container or a humidity dome can be used to maintain a relative humidity level of 80% or higher, which encourages root initiation. Place the newly potted material in an area that receives bright, indirect light, such as a north or east-facing window. Temperatures should be kept consistently warm, ideally between 70°F and 80°F, as fluctuations stress the cutting and inhibit growth. Good air movement is necessary; if using an enclosed container, open it daily for a few minutes to exchange the air and reduce the risk of mold.
Transitioning the New Plant
The cutting is ready to be moved from the humid rooting environment once it has developed sufficient new root growth. For keikis, this means the new roots are at least one to three inches long and actively growing. For backbulbs, the transition occurs once a new shoot has emerged and its own roots have begun to form. Moving the plant too early, before a robust root system is established, will result in a failure to thrive.
The new plant should be potted into a small container appropriately sized for its root mass, often a four-inch pot for a keiki. The potting medium should transition to a coarser, well-draining mix, such as a standard orchid bark blend, which is better suited for mature root systems. The acclimation process requires slowly reducing the ambient humidity and gradually increasing the light exposure over several weeks to prevent shock. Once new leaves and roots are actively growing in the new medium, a weak solution of balanced orchid fertilizer can be introduced to support continued development.