Any of you ever deal with a fruit tree that wont grow naturally from a seed? I have come across one such tree by the name of Spanish plum, red mombin
and have read
"Of great interest is the absence of seed formation in this species, an aspect that was first studied in the Philippines. In the "nut", which occupies the central part of the fruit, only remnants of aborted seeds are found. This is due to both poor pollen formation and the oosphere. Natural distribution is thus completely limited, but the ease with which stems and branches sprout, together with their fragility, allows a very limited natural propagation. Recognition and conservation of the numerous variants which this species displays is possibly due to the action of humans."
What I want to know is: How can I plant this tree from the seed? There has to be a way, right?
From the quote you have I'd suggest that finding a fertile seed would be very rare - this is probably the equivalent of trying to grow a grape vine from a "seedless" grape variety. There will be partially formed seeds, but nothing actually viable to germinate from.
You may find one seed in a hundred that is viable (no guarantee) - but that would not be likely to breed true to the original.
Moderator, Treatment Free Beekeepers group on Facebook.
Maybe you could find a closely related plum that does have fertile seeds, plant it within pollination distance from one of the ones that doesn't make fertile seeds, and hope for a crossbred seed that is fertile, then work your way up from there, continuing to pollinate the ones that are closest to the desired tree but still make fertile seeds.
From the snippet you quoted it seems like the primary issue is pollination. Try hand pollination for as many flowers as you can manage, using as many plants as possible in case they are not self fertile. Get a paintbrush and pretend your a bee. Maybe a heavy pollination will yield seeds?
The only way to get it start from seed is to make it have seeds.