To confirm the registration of an Australian native hybrid & view its composition/progeny: (Database as at 1st April 2018 RHS registrations)
For non-Australian Dendrobium hybrids use the Dendrobium Hybrids checklist here
Sarco. Sweetheart= Fitzhart x Heidi ( has 22 hybrid progeny ) registered: 26/05/1998 by Clement R. -Batchelor S.
Sarco. Sweetheart ‘Wave’ AM/AOC 2014
Species composition summary:
Sarco. Sweetheart = Fitzhart x Heidi = [hartmannii x fitzgeraldii] x [Fitzhart x hartmannii]
Fitzhart = hartmannii x fitzgeraldii