It is among the top hard-to-germinate genera (Hidayati 2012). The coat is thick and woody. The seed has to undergo a process of growth inside the coat. At some point it is so tight and cramped that it pops out and live on its own producing butter flowers. Many of them to see in Kings Park Botanic Park at this moment:
Reference: Hidayati, S., and J. Walck. 2012. Guinea flowers (Hibertia) and the complexities to germinate them. For People & Plants (77):18-19.