This is a very large genus of some 900 species and very many cultivars and hybrids. They come from tropical and subtropical regions and are used either as houseplants or treated as annuals as they cannot withstand winter temperatures that sink to freezing and below.
Many of the house plants are forms of Begonia rex. The tuberous begonias, so called because of their tuberous roots, can be used indoors or outside in containers. These include the multiflora types that form large double flowers that are very brightly coloured. They are a fascinating group and many gardeners are so enchanted with them that they build up large collections of different forms.
Another popular type is that based on Begonia semperflorens. These, again, can be used inside or out. In the former they are usually grown as individual plants, but outside they can be used in vast numbers as bedding plants or in smaller quantities in containers. The ones used outside can be over wintered under warm glass.
Like most plants that grow under glass, begonias are subject to a wide range of pests and diseases, but with vigilance these problems can be overcome. Those used outside are grown either in good soil for beds or a good quality potting compost in containers.