Orchids are often found growing on trees or rocks in their native environments. This characteristic, known as being epiphytic, necessitates a specialized approach to their care and propagation. Most orchids are traditionally grown in a coarse mixture of bark or moss to mimic the airy conditions of their natural habitat. While their biology suggests a high risk of failure, specific techniques can make water propagation a viable method.
The Suitability of Water for Orchid Propagation
Orchids are not typically submerged in water due to their specialized roots. These roots are covered in a spongy, white layer called the velamen, which quickly absorbs moisture and nutrients. The velamen is adapted to rapidly soak up water and dry out quickly, which is crucial for survival.
When roots are constantly submerged, the velamen remains saturated, preventing the necessary gas exchange and suffocating the tissue. This lack of oxygen creates an anaerobic environment, leading to bacterial and fungal issues known as root rot. Specific methods, such as “semi-water culture” where only a portion of the roots is submerged, address this by ensuring adequate airflow. Certain types, particularly Phalaenopsis and Dendrobium species, can adapt to high moisture by growing new roots suited to aquatic conditions.
Detailed Methods for Water-Based Propagation
Propagating orchids in water is most successful using plantlets called keikis, or specific stem sections from cane-type orchids. A keiki is a small clone that develops directly on the flower spike or a cane node of the parent plant. Remove a keiki only once it has developed at least two or three leaves and three or more independent roots that are one to three inches long.
To prepare the keiki, sterilize a razor blade or sharp shears with rubbing alcohol. Cut the plantlet from the parent spike, leaving a short section of the stem attached below the roots. Treat this stem stub with cinnamon, an antifungal agent, and allow it to dry for several hours to form a protective callus.
The prepared keiki is then placed into a narrow, clear glass container. The base of the plant should rest on the rim so only the very tips of the roots touch the water. This semi-submerged setup allows the plant to draw moisture while the majority of the root structure remains exposed to air, preventing rot.
Essential Care and Management in Water Culture
Maintaining an orchid in water culture requires careful attention to water quality and circulation. Tap water often contains high levels of dissolved minerals and salts that can build up on the roots and harm the plant. Using distilled, filtered, or rainwater is preferred to avoid this mineral accumulation, which can cause root burn.
The water should be changed weekly to prevent the development of harmful bacteria or algae that thrive in stagnant conditions. When refreshing the water, add a highly diluted specialist orchid fertilizer at one-quarter of the recommended strength.
Environmental Factors
The practice of allowing the roots to dry out completely for a few days between water applications, known as the soak-and-dry method, ensures the roots receive necessary oxygen. Place the container in a location that receives bright, indirect light. Maintain temperatures between 70 and 80 degrees Fahrenheit during the day to encourage active growth.
Transitioning the Propagated Plant to a Permanent Medium
The roots developed in a water-based system are delicate. Once the propagated plant has a robust root system, transition it gradually to a traditional, permanent potting medium to prevent severe transplant shock.
Begin by moving the plant into a small pot filled with a fine-grade orchid mix, such as fine bark and sphagnum moss. For the first few weeks, keep the roots wetter than a mature orchid’s roots to acclimate the water-grown tissue to a less moist environment. Gradually reduce the watering frequency until the new plant establishes a normal routine, allowing the medium to dry slightly between applications.