I think this may have been what ive seen. But i thought they wanted people to register all gardens maybe i was thinking of something else.Maybe you heard about this program?
https://www.usda.gov/peoples-garden/what-pg
Yes, they are encouraging people to register "people's gardens." But those are gardens run by a group of people. They will not let you register your own private garden even if you wanted to:
The kind of gardens they do want:
(Both quotes taken from the page I linked to, on the USDA official site.)