So theres a nearby area that would support a Desmanthus leptolobus population, and I might even try it in my grass-lawn since they look lawnmower impervious, what I'm unsure of is when to best scatter some seed about for mass plantings (in semi-arid zone 7a).
I hoe the bejeezus out of my herb garden in the fall and spring so I never noticed if seed dropped when ripe (now) has a reasonable success rate by the following spring. It looks like a local weed when young so I just kill everything not in the Desmanthus spot.
Number of seeds on hand isnt really an issue, its just a matter of deciding if I should scatter about 400 seeds in the fall and 400 in the spring, or save all 800 spare seeds for spring

Any experiences?

Sorry to bump an old post but I have a possibly useful answer?
Seeds naturally drop by some point during August and can find their way into cracks in the earth which is often dry at that hot time of year but rains following hurricanes are also common in the period from June through November.
Grass provides perfect shelter for seedlings also.
That is when I'd sow seeds if not planning on transplanting.