Moringa won't make pods?

I've been growing moringa trees for almost four years now. I've grown most of mine from seeds since those seem to be stronger than the ones I started from cuttings; however, there's a problem.

They don't make pods.

I planted PKM1, which is supposedly the best type for quick pod production, yet I'm still not getting anything. I've wondered if the issue is pollination, since they do bloom, but I don't know. They'll flower every year, sporadically, then the blooms will fall without giving me any pods.

The same thing has happened with the moringa trees down in The Great South Florida Food Forest Project. Who knows?

I've asked around about this problem and have seen something interesting: folks are getting pods from them even up here in North Florida, but I'm not. On further inquiry, most of the success stories I'm hearing about involve pods being produced on trees that are either growing in stressed conditions or in containers. My guess is that the restricted root development/tough surroundings are pushing the trees to produce seeds.

This makes sense. Stress induces a race to reproduce in quite a few species, including our own.

Ticking biological clocks = OMIGOODNESSINEEDABABYNOW!!!

I think I need to try keeping some moringas in pots to see if this theory is correct. I'm also going to plant more seeds in the spring from alternate seed lines. I have some seeds from Thailand (thank you, ebay) and some from Jamaica (thank you, Rycamor). I also have some from my friend Cathy. Here's a pod she brought over to share the other night:

Though moringas look like they'd be a nitrogen-fixing tree from the bean and pea family, they're not. They're the own thing, as you can tell from the differently shaped pods and seeds.

Anyone have any good tips on getting moringas to set seed?