Begonias (Begoniaceae), with their salmon, red or pink blooms and oftentimes frilly petals, have come a long way from their long-suffered reputation as a “grandma’s garden” flower. New hybrids have exciting textures and colors, lending gardens a more sophisticated look. Landscapers and gardeners are using begonias in their flower beds and as potted outdoor plants more often these days, as the plants add color and texture to flower beds and are readily propagated. From seeds to tubers to tip and leaf cuttings, propagation of begonias can be fairly simple. If started in the winter, begonias will provide the shady areas of your garden with delightful blooms come spring.
Planting begonia seeds is the simplest method of propagation. Cover a seed flat with potting soil. A mixture of equal amounts peat moss and Perlite works well. Place seeds across the surface of the potting soil, sprinkling between your fingers like you would sprinkle salt over a dish. The seeds are fine and do not need to be covered with potting soil. Mist the surface. Place a sheet of glass directly over the planted surface. A plastic wrap covering can be used as well. Place in diffuse light for seven days. Mist as soil dries out. Remove glass when green seedlings can be seen. Continue misting as plants grow, or water lightly. Snip off leaves at 10 weeks of age. Pot tubers into 4-inch containers at 12 weeks. Keep indoors until threat of frost has passed.
To plant already existing tubers, prepare a seed flat with Perlite or peat moss. Find the depression on the tuber: this is the upper surface. Place the tuber upright in the potting substance, and cover lightly with the potting medium. Keep the begonia tubers moist but not overly wet. Water condensing in the tuber’s depression can cause the plant to rot. Allow to grow under diffuse light, maintaining a temperature of around 70 degrees F.
Where cultivating begonias gets exciting is by the method of cuttings. For tip cuttings, select a stem with a bud in the leaf node (a small bump above the stem segment). Cut 1/2 inch below the bud, and place begonia stem in water. Pot the cutting in a 4-inch pot filled with potting soil after several roots form. Segments of the stem can be cut and placed in water as well but may be prone to rotting.
Many begonias are readily willing to grow from leaf cuttings, a fascinating process. With clean garden shears, remove a leaf or a portion of a leaf. If removing a portion of a leaf, keep a main vein in the cut segment. Place the cutting upright in potting soil. Mist, and cover with plastic wrap to ensure humidity. Begonia expert Brad Thompson suggests sterilizing the cuttings by dipping them into a mixture of 5 percent bleach, then again in water before planting.