I think this is bred by hybridisation Myriam, that is by crossing species or hybrids or both.
The RHS has the preferred name Begonia 'Pin Up' but there is an entry in the plant file for Flame.
Tuberous Begonia (Begonia x tuberhybrida Pin-Up® Flame)
The science library has it as Begonia tuberosa 'Pin Up'
I can't find it listed in the plant finder on the RHS, but their feature page should give the correct name, which is Begonia 'Pin Up' or maybed you could call it Begonia 'Pin Up Rose'
I found the full details, Pin-Up is the registered trade mark.
http://www.provenwinners.com/p...
Common name: Tuberous Begonia
Genus: Begonia
species: x tuberhybrida
Cultivar: Rose
Trade name: Pin-Up
