I have found some APIs to determine when foods are in season but they most a secondary feature and not very accurate. Their geographic area will be as large as the United states. I need something for local food shopping.
It doesn't appear to be offered as data, but it would be exceedingly easy to scrape this Eat Local resource from NRDC. There's a page for each state which lists foods by month.
For each state they have "learn more" links, which probably also lead to their data sources (few of which appear to be structured data.)
you could try usda farmer's market api.
"listings to include: market locations, directions, operating times, product offerings, accepted forms of payment, and more"
read more here: