All non-tuberous begonias are frost-tender. For optimal growth, temperatures between 54�F (12�C) and 76�F (24�C) are required. Although they like good ventilation (which helps prevent mildew), they do not like cold winds. Fortunately, there are many that grow well indoors and some that are suited to container culture only, so even growers in cooler areas can enjoy these plants year-round as houseplants, and in conservatories or terrariums. Wherever they are grown, good light is essential. Morning and afternoon sun will help give good foliage color, prevent legginess, and improve the quality and quantity of the flowers. For best results avoid dark corners. Humid conditions of around 40-60 percent are ideal. In the house as container plants, the humidity can be increased by setting the container over, but not in, water, e.g., by placing the pot on some pebbles in a saucer. This is particularly useful in the winter if the heating system is drying out the atmosphere. All begonias prefer free-draining soil and, if grown in containers, a free-draining open mix. Beware of over-watering container-grown plants. Water should be given only when the mix is dry to the touch, but then it is important to add enough water to thoroughly moisten the mix. Care should be taken, however, to avoid watering the leaves. Every few weeks during the growing season, a weak liquid fertilizer may be applied, but only when the mix is damp, or the roots will burn. Such applications should cease during the dormant period (winter). Pinching out improves branching and bushiness, and pruning improves the shape. Damaged or aging leaves and spent flowers should be removed. In general, these plants are remarkably free of disease. Attention to the above requirements will go a long way toward preventing mildew, the main problem that can occur.
All begonias, mentioned below, are suitable for container culture and may be grown as houseplants.