Some begonias are prized for their flowers, others for foliage, still others for both; most are easy to grow. They are categorized by their manner of growth: those that have tubers (tuberous begonias), those with fibrous roots, and those with rhizomes-horizontal surface stems that send up leaves and flowers. Starting begonias Nearly all begonias grow readily from stem cuttings; the rhizomatous kind grow from divisions of the rhizomes.
Some, such as rex begonias, can be grown from leaf cuttings. Wax begonias can be started from seeds. Scatter the tiny seeds on top of fine-sifted potting soil and press them down gently. Set tubers, hollow side down, in loose peat moss or peat moss and sand with their bottoms at the surface.
Cuttings and tubers should be started indoors about 2 to 3 months before outdoor planting time. Cover the trays or pots with plastic wrap punched with a few airholes. Keep them warm, slightly moist, and shaded from direct sunlight. When tiny plants (from seeds) or 1-inch shoots (from tubers) appear, move them to individual pots, turning tubers hollow side up. At this time tubers can be divided; cut them with a knife, leaving one or more buds to each section. Dip the cut surfaces in a fungicide such as powdered sulfur.
When all danger of frost is past, move tuberous begonias intended for outdoors to a cold frame. Later, when the soil stays warm (50°F to 55°F) overnight, set the plants in a shady spot with loose, well-drained soil enriched with compost or peat moss. Apply a balanced fertilizer, such as 510-5; water with a wand to keep moisture off the leaves. Some begonia favorites Tuberous begonias have huge single, double, or semidouble blooms on 1 to 2-foot-tall plants. They are spectacular indoors or out, in beds or in pots. Trailing tuberous begonias do well in hanging pots in shaded locations. Rex begonias, which are rhizomatous, are grown for their beautiful leaves colored in pinks, reds, and greens. They make excellent bedding plants for shade.
Wax begonias-the common bedding plants-bear small white, pink, or red flowers until frost. They like brighter light than other begonias, but not direct sun, and sometimes seed themselves. In fall you can pot the seedlings for indoor bloom.
Indoors, all begonias require room temperature and strong light, but not direct sun except in winter. Provide humidity by placing the pot on gravel in a saucer or tray with water not quite covering the gravel. Check the soil every few days; water when dry.
To save tubers, dig them up before frost, store them in a dry place until the foliage has died, then clean and store them at 50°F to 60°F