orons is needed for the growth of the pollen tube during flower pollination and is therefore important for good seed set and fruit development (factsheet).
I spent much time looking at the recalcitrant plants and it is hard not to ask yourself a question: Why to produce such nice flowers if you stay infertile? I have not found any literature on native plants but there is a big pile of evidence for agricultural crops in respect to boron deficiency. It is a micronutrient much-needed in the process of seed production.
Add to it the fact that Boron is easily leached from the sandy soil in region of high rainfall and we can be on the way to discover a way to make south-western plants “have sex” again.