Seemingly infinite variety characterizes the genus Begonia. The flowers often resemble roses or carnations, and they rarely disappoint growers. But I have to be selective in what I grow for my own pleasure. They come in strong primary colors and great pastels, and they bloom constantly, from summer until frost. I don't know of anything else with the same combination of flower size and shape that blooms in the shade.
Colors range from white through yellow, orange, apricot, pink, and red.
Some have bicolor petals, such as white with a pink edge or yellow with a red edge. Begonias with petals that are edged in lighter or darker colors are called picotee. Buy dormant tubers in winter, either by mail from a specialty nursery or from a nursery or garden center. Another possibility is to buy blooming plants in summer. Most gardeners buy dormant tubers, which are easier to grow than seed and less expensive than blooming plants.