Wax begonia, scientifically known as Begonia semperflorens, is a popular bedding plant frequently grown as an annual, though it is a perennial in warmer climates. Propagating these fibrous-rooted plants is a common practice for gardeners seeking to multiply their favorite varieties or ensure a continuous supply of flowers. Both vegetative reproduction through cuttings and sexual reproduction via seed starting are effective methods for increasing your stock of this versatile plant.
Essential Preparation and Timing
The optimal time to begin propagating wax begonias is during late winter or early spring. Start seeds indoors approximately 10 to 12 weeks before the last expected frost date. Stem cuttings can be taken in early spring or early summer from actively growing, non-woody stems.
Success depends heavily on using sterile equipment and a high-quality, sterile growing medium to prevent fungal diseases. You will need sharp, clean scissors or a knife for cuttings, small pots or seed trays, and a well-draining mix, such as a blend of peat moss and perlite or a commercial seed-starting mix. Environmental conditions must be controlled, ideally providing a consistent warm temperature between 70°F and 75°F for rooting and germination. High humidity is also beneficial during the initial rooting or germination phase, which can be achieved using clear plastic bags or humidity domes over the containers.
Propagating Through Stem Cuttings
Stem cuttings are the preferred method for creating clones, ensuring the new plants possess the exact characteristics of the original. Select a healthy, non-flowering stem section that is approximately 4 to 6 inches long from the tip of the plant. Make a clean cut just below a node, which is the slightly swollen point on the stem where a leaf is attached, as this is where the highest concentration of root-forming cells is located.
Carefully remove the lower leaves from the cutting, leaving only two or three leaves at the top to minimize water loss through transpiration. Dipping the cut end into a powdered or liquid rooting hormone can accelerate the development of new roots, though it is not strictly necessary for begonias. Insert the prepared cutting into a hole poked into the pre-moistened rooting medium, ensuring at least one node is buried beneath the surface.
Firm the medium gently around the stem to secure the cutting and provide good contact with the medium. Cuttings can also be rooted in water, but the roots that develop may struggle to transition to soil later. Place the planted cutting in a location with bright, indirect light and maintain a humid environment with a plastic cover. Roots should typically emerge within a few weeks.
Propagating Through Seed Starting
Growing wax begonias from seed allows for the production of many plants at once, though the process is slower. Since begonia seeds require light to germinate, they must be surface-sown and not covered with soil. Fill a seed tray with a fine, sterile seed-starting mix and moisten it thoroughly before sowing.
Sprinkle the dust-like seeds lightly and evenly across the surface of the medium, then gently press them down to ensure good contact with the moist soil. Covering the tray with a clear lid or plastic wrap will maintain the high humidity and consistent moisture necessary for germination. Place the covered tray in a warm spot, ideally around 70°F to 75°F, under bright fluorescent or LED grow lights for 14 to 16 hours daily.
Germination is slow and can take anywhere from 14 to 28 days for seedlings to emerge. During this period, avoid letting the surface of the mix dry out, misting gently to keep it uniformly damp. Once the initial green leaves appear, continue to provide consistent light and warmth while maintaining high humidity.
Initial Care for Newly Rooted Plants
Once cuttings have developed a robust root system, or seedlings have produced their first set of true leaves, they are ready for the next phase of care. For both cuttings and seedlings, the first step is to begin the process of gradually reducing the high humidity. This is done by slowly venting the plastic cover or dome over a period of several days to a week, which acclimates the new roots and leaves to normal air conditions.
When the young plants are sturdy enough, they should be transplanted into individual small pots, 3-inch containers, using a general-purpose potting mix.
Before moving them outdoors permanently, the plants require a hardening off period to adjust to direct sunlight, wind, and temperature fluctuations. This involves placing the pots in a sheltered outdoor location for a few hours each day, progressively increasing the duration over a span of seven to ten days. Once fully hardened, the new wax begonias can be planted directly into the garden or their final containers after all danger of frost has passed.