"IMHO" there are a lot of well known problems with carbone datation. You can read about it in scientific journals and make your own opinion.

Any measurement can have errors of methodology, and a wrong measurement does not have any value. Don't worship numbers just because they seem fancy or fit with a narrative. They are just that, a number.

Without a genetical analysis we can not know if a plant variety is lost, or just forgotten, or a clone of a extant variety buried ten years ago. Show me the analysis before to start talking abour old ruins, caravans and lost cities.