Rieger begonias (B. × hiemalis), often called Elatior begonias, are hybrid begonias, originally derived from a cross between summer-flowering tuberous begonias (B. × tuberhybrida) and a rarely cultivated winter-flowering species, B. socotrana starting as far back as 1883. The name Rieger, now applied to all of them, comes a series introduced in 1955 from German hybridizer Otto Rieger. The alternate name, Elatior begonia, likewise derives from a once popular strain otherwise largely forgotten.Elatior begonias (Begonia x hiemalis) adorn homes across much of the United States, as these flowering plants are available year-round from florists and greenhouses. Typically grown as a summer annual, this plant can be grown outside in a sheltered location where temperatures range from 50 to 75 degrees Fahrenheit.