if you're planting seeds. count on 2 years for first fruits to harvest. 3 years for a decent crop.
if you start from saplings, 18 months or less to first harvest, better harvest per year afterwards.
my suggestion, buy saplings instead of seeds, by year 3 you'll be selling both saplings for others who get interested, and seed for biodiesel.
South Texas Jatropha Farms.
