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. Colonial Hart= serrulatus x Fitzhart ( has 2 hybrid progeny ) registered: 23/12/2002 by Spence P.
Species composition summary:
Sarco. Colonial Hart = serrulatus x Fitzhart = serrulatus x [hartmannii x fitzgeraldii]