Answer:
Sweet potato seeds.
Step-by-step explanation:
Sweet potato is a plant originating from the Americas and it wasn't until after the discovery of the new continent that it spread all over the world.
However, there seems to have been a more ancient contact with the Americas, well before the European discoveries. Seeds of sweet potatoes were discovered on the Cook islands, proving to date as far as 1000 AD. This suggests that Polynesians could have established some pre-Columbian contact and trade with Native Americans.