Alocasia Black Velvet (Alocasia reginula) is a tropical houseplant known for its striking, near-black, velvety foliage. Native to Borneo, its compact size makes it ideal for indoor cultivation. Like many related aroids, it propagates and stores energy using specialized structures called corms. A corm is a swollen, underground stem base that functions as a storage organ for starches and nutrients, enabling the plant to survive periods of stress or dormancy.
Locating and Harvesting Alocasia Corms
The ideal time to harvest the small offset corms, often called cormels, is during routine repotting or when the mother plant enters dormancy. Harvesting while the plant is out of its container minimizes stress, as the root system is fully exposed. Cormels are typically found attached directly to the main corm or nestled within the roots just beneath the soil line. They appear as small, firm, pale brown or white nodules.
Careful removal is necessary to avoid damaging the mother plant’s root system or the cormels. Gently brush or wash away the soil to identify where the cormels are attached. Use a sharp, sterilized cutting tool, such as a scalpel or small pair of scissors, to sever the connection cleanly. Sterilization, often achieved by wiping the tool with isopropyl alcohol, prevents the transfer of pathogens or fungal spores.
After separation, the mother plant should be immediately repotted into fresh substrate. The harvested cormels range in size, from a small pea to a marble, and larger cormels generally have a higher success rate. Handle the cormels gently, ensuring the outer protective layer remains intact before preparation.
Preparing Corms for Propagation or Storage
After harvest, the cormels must be thoroughly cleaned to remove residual soil particles and dead root remnants. Excess debris can harbor fungal spores or bacteria, significantly increasing the risk of rot during the initial propagation phase. A gentle rinse under running water, followed by a soft scrub, is usually sufficient to expose the smooth, firm surface of the corm.
Before planting, the corms must undergo curing, which allows the small wound created by the separation to dry out and form a protective layer called callusing. Lay the cleaned corms in a dry, well-ventilated location away from direct sunlight for 24 to 48 hours. This protective barrier seals the corm, preventing moisture loss and blocking the entry of potential pathogens.
To safeguard against rot, dust the callused corm with a common household spice like cinnamon powder, which possesses natural fungicidal properties. Alternatively, a commercial fungicide designed for bulbs can be applied for enhanced protection. If immediate propagation is not possible, corms can be stored in a cool, dark environment, ideally between 50°F and 60°F. Store them nestled within a breathable medium like slightly moistened peat moss or vermiculite. This storage method keeps the corm dormant and viable for several weeks or months.
Step-by-Step Guide to Sprouting Corms
The successful sprouting of Alocasia corms relies on providing a tropical microclimate, mimicking the warm, humid conditions of their native habitat. If the corms have been stored or appear slightly shriveled, soaking them in lukewarm water for a few hours prior to planting can help rehydrate the tissues and signal the breaking of dormancy. The choice of propagation medium is flexible, but it must offer both excellent moisture retention and high aeration to prevent suffocation or rot.
Popular choices for sprouting include sterilized and inert media:
- Sphagnum moss
- Perlite
- A combination of the two
Place the corm in a clear container filled with a slightly damp, not soaking wet, medium. This allows for easy monitoring of root and shoot development. When positioning the corm, identify the growing tip, which often appears as a slightly pointed end or a small cluster of concentric rings.
The corm should be planted with the growing tip facing upward, positioned just barely beneath the substrate surface. Some growers prefer placing the corm horizontally, which also works effectively. The entire container should then be sealed or placed inside a humidity dome to create an enclosed environment that traps moisture.
Maintaining a consistently high temperature is the most influencing factor in successful sprouting, as these corms require warmth to activate their growth hormones. The ideal temperature range is 75°F to 85°F (24°C to 29°C), which often necessitates the use of a specialized heat mat placed beneath the propagation container. This elevated temperature, combined with high humidity inside the dome, simulates the forest floor conditions that trigger rapid germination.
Under optimal conditions, the corm will first develop a fine network of thin, white roots from its base, sometimes within two to four weeks. Following the emergence of the root system, a small, pale green shoot will begin to extend from the upward-facing tip. Sprouting time can vary widely, from as little as three weeks to several months, depending on the corm’s size, its state of dormancy, and the environmental stability of the setup. Consistent monitoring is required to ensure the medium remains lightly moist and that no condensation pools excessively, which could encourage fungal growth.
Nurturing the New Alocasia Plantlet
Once the corm has produced its first true leaf, the new plantlet is ready to transition from its high-humidity environment. This transition must be gradual; slowly acclimate the plant to ambient room humidity over several days by opening the dome or container lid for increasing periods. Moving the plant too quickly can shock the new growth, causing the first leaf to shrivel or brown.
The plantlet requires bright, indirect light to fuel subsequent leaf growth, but avoid direct sun exposure to prevent scorching. Initial watering should be careful, allowing the top layer of the medium to dry slightly before reapplication. When the root system is established and the second leaf begins to emerge, the plantlet can be transferred into a slightly larger pot containing a well-draining, chunky aroid potting mix.