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.Originally, Rieger begonias were winter-flowering (that’s what hiemalis means!), needing short days in order to bloom, and they were, in fact, commonly called winter begonias. But over time, everblooming begonia species were added to the hybridization palette and most modern hybrids, like the Solenia, Valentine, Dragone, Frivola and Glory series, are day-neutral and essentially everblooming.