"Radiocarbon dating shows kūmara were being stored in pits on the Otago coast in the 15th century, seemingly overturning assumptions the area was too cold to store live Polynesian crops. ....

https://www.stuff.co.nz/science/124941758/study-shows-kmara-stored-in-otago-coast-pits-in-15th-century-may-even-have-been-grown-there