Orchid multiplication is the process of generating new plants from a single parent specimen. This practice is common for gardeners seeking to increase their stock or rejuvenate an older, overgrown plant to maintain its vigor. Orchids are broadly categorized into two main growth types, which dictate the most effective multiplication method. The first is the sympodial type, which grows horizontally and sends up new vertical shoots. The second is the monopodial type, which grows upward from a single, central stem.
Essential Preparations Before Multiplication
Before beginning any propagation procedure, careful preparation of tools and materials is important for success and plant health. You will need sharp cutting instruments, such as a sterile razor blade, a clean knife, or pruning shears, to make clean incisions that heal quickly. Fresh, appropriate potting media and containers should also be ready, as the new divisions or cuttings must be potted immediately after separation.
Sterilization of all cutting tools is necessary to prevent the transmission of viruses and fungal or bacterial diseases between plants. Tools can be sterilized by soaking them for 30 minutes in a solution of one part bleach to nine parts water, or by wiping them with 70% to 100% isopropyl alcohol and allowing it to air dry completely. Metal blades can also be quickly sterilized by heating them with a flame until they are nearly red hot, which is particularly effective against viruses. The best time to perform propagation is typically when the orchid has finished blooming and is just beginning a new period of active vegetative growth, often coinciding with repotting.
Propagating Orchids by Division (Sympodial Types)
Division is the most reliable method for multiplying sympodial orchids, which include popular varieties like Cattleya, Cymbidium, and Oncidium. These orchids grow along a horizontal stem called a rhizome, producing thickened storage organs known as pseudobulbs. The goal of division is to separate the plant along this rhizome into smaller, self-sustaining units.
To begin, gently remove the entire plant from its pot, which is easiest when the potting mix is slightly moistened. Carefully remove the old potting media from around the roots, untangling them as much as possible. Use sterile cutters to trim away any dead or mushy roots. You must then locate the rhizome connecting the pseudobulbs to determine the cutting points.
It is necessary to ensure that each new division retains a minimum of three to five healthy pseudobulbs. This number is crucial because the pseudobulbs store the water and nutrients needed to support the new division while it establishes a fresh root system. Divisions with fewer than three pseudobulbs are less vigorous and take significantly longer to mature and flower.
Use your sterilized cutting tool to sever the rhizome between the groups of pseudobulbs, making sure each section has a viable growing point or “eye.” Once separated, the cut surfaces of the rhizome can be dusted with a fungicide powder or cinnamon to help seal the wound and prevent infection. Each resulting division is a genetically identical replica of the parent plant, ready for its own container.
Multiplication Using Keikis and Stem Cuttings (Monopodial Types)
Monopodial orchids, such as Phalaenopsis and Vanda, grow upward from a single stem and lack the pseudobulbs used for division. Multiplication for these types relies on keikis, which are naturally occurring offsets or plantlets, or through stem cuttings. Keikis are genetic clones that often appear on spent flower spikes or occasionally at the base of the plant.
Propagating Keikis
To remove a keiki, you must wait until it has developed its own leaves and a sufficient root system. This typically occurs when the roots are at least one to two inches long and there are a few mature leaves. Use a sterile razor blade to cut the keiki from the main stem, leaving a small piece of the parent stem attached to the plantlet for support. This small, independent plant can then be potted directly into its own small container.
Using Stem Cuttings
Stem cuttings are primarily used for certain monopodial types like Vanda or Phalaenopsis that have grown very tall. In this technique, the main stem is cut, often below an aerial root, to create a top cutting with several healthy roots attached. The remaining base portion of the plant may be left in its pot, as it often develops new growth shoots from dormant stem cells. For some orchids, like Dendrobium, a spent cane or stem is cut into smaller sections, each containing at least two nodes. These sections are laid horizontally on moist sphagnum moss to encourage new growth from the nodes. Applying a rooting hormone to the cut ends is an optional step that may encourage faster root development.
Establishing New Plantlets: Initial Care
The first few weeks following propagation are the most important for the survival of the new plantlets. All new divisions, keikis, and cuttings should be potted in fresh, well-draining orchid media, such as bark chips, charcoal, or sphagnum moss, which are specifically designed to allow air circulation around the roots. Using an appropriately sized pot, which is often small, prevents the root system from being overwhelmed by an excessive volume of potting material.
The freshly cut surfaces need time to dry and heal before being exposed to moisture. Therefore, you should withhold watering for three to five days immediately after potting. After this initial dry period, water sparingly, only moistening the media when it has nearly dried out completely.
The new plantlets will benefit greatly from a warm environment with high humidity, ideally above 60%. This can be achieved by placing the pots in a humidity dome or a clear plastic bag. Place the new pots in a location that receives bright, indirect light, avoiding any direct, harsh sunlight that could scorch the leaves. Good air circulation is also necessary to prevent the development of mold or fungal issues, especially in a high-humidity setup. Once the new growth shows active root and leaf development, you can gradually transition the plantlet to the normal care routine of a mature orchid.