Propagating a new orchid from a stem section, known as asexual reproduction, is a rewarding way to multiply your collection. This method bypasses the complexity of growing from seed and creates a new orchid that is a genetic clone of the parent plant. Successfully rooting an orchid stem requires careful preparation, a controlled environment, and patience while the cutting develops its own independent root system. This guide focuses on the practical steps necessary to encourage root growth from a prepared cutting or plantlet.
Identifying the Propagating Material
The term “stem” in orchid propagation refers to two distinct types of material: a keiki or a section cut from the flower spike. Keikis (Hawaiian for “baby”) are small, fully formed plantlets that naturally develop on the flower spike, commonly seen in Phalaenopsis and Dendrobium species. These plantlets are mini-clones with leaves and often aerial roots, making them the most straightforward material to root.
The alternative is using a section of the flower spike itself, which contains dormant nodes that can be stimulated to produce a new plant or keiki. This method is typically used when a natural keiki is not present and requires applying a specialized hormone paste to the node. Unlike a keiki, a spike cutting has no pre-existing leaves or roots and must rely entirely on its stored energy to initiate new growth. For orchids with a cane-like stem structure, such as many Dendrobium types, the cane can be cut into sections containing nodes for propagation.
Preparing the Cutting for Root Growth
Proper preparation is necessary before placing the material into a rooting medium to prevent infection and maximize success. First, sterilize all cutting tools, such as a razor blade or sharp shears, with alcohol or a flame to avoid transmitting pathogens. When removing a keiki, cut the flower spike about one to two inches above and below the plantlet to create a handle for planting.
All cut surfaces on the mother plant or the cutting must be sealed immediately to prevent fungal or bacterial entry. Ground cinnamon powder is often used as a natural antifungal; dab it directly onto the fresh cuts of both the parent plant and the separated section. For a spike cutting, apply a specialized rooting hormone paste or powder directly to the node you wish to activate. Allow the cutting to cure for a few hours in the open air, permitting the cut surfaces to dry slightly before planting, which reduces the risk of rot.
Step-by-Step Rooting Methods
The two most effective methods for encouraging root growth involve maintaining high, consistent humidity around the cutting. One common technique is the Sphagnum Moss Method, where the cutting is placed in a small container filled with lightly moistened, high-quality sphagnum moss. After soaking the moss, gently wring out the excess water until it is damp but not saturated. Carefully nestle the cutting into the medium, ensuring any existing roots are covered but the base of the plantlet remains exposed. The container should be placed inside a clear plastic bag or covered with a clear dome to create a humid microclimate, with small holes for air exchange to prevent mold growth.
A second viable option is the use of a humidity chamber, often referred to as a “Keiki Box,” which is ideal for spike cuttings that have not yet formed a plantlet. In this method, the spike section is suspended above, or partially wrapped in, a bed of moist medium like sphagnum moss or perlite inside a sealed clear container. This setup provides near-100% humidity while ensuring the cutting is not sitting in standing water, which prevents rotting. Both methods require placement in an area with bright, indirect light and a stable temperature, ideally between 70 to 80 degrees Fahrenheit. Root development can take several weeks or even months.
Transitioning the New Plant
The young orchid is ready for transplanting when its new root system is mature. A keiki or spike cutting should have developed at least two to three leaves and roots approximately one to three inches long. These roots must show healthy, firm green tips, indicating active growth and the ability to absorb water independently.
To transition the new orchid, gently remove it from the moss or rooting chamber and plant it in a small pot, typically four inches in diameter. Use a permanent orchid potting medium, such as a bark and charcoal mix, that is slightly finer than what is used for a mature orchid due to the delicate young roots. For the first few weeks, “harden off” the new plant by gradually reducing the surrounding humidity. This adjustment prepares the orchid for the drier air of a typical home environment.