bigdog

They don't look a whole lot like each other, but they are still both Ensetes. I can assure you of this: They are both very difficult to germinate. I see RPS has fresh seeds now too. I'm almost tempted, but I just bought several hundred other seeds from them. Ahhh...

The habit of growing on limestone cliffs is interesting. Sounds like the seeds somehow get deposited there, and probably sit there for quite some time. The monsoons might trigger them to germinate. There is a cactus, Ferocactus I think, that requires gibberellin in order to germinate. They grow on rocky outcroppings, and the seeds must land in a crack on top of some leaf litter. When the rains come, fungus will grow on the litter, and then the cactus seeds will germinate.

There is also the thought that repeated cycles of wet, then hot and dry, could weaken the seed coat enough to allow water to penetrate it. Works for some palm seeds.