Seeds and pollen collected by archaeologists in Ohio are turning out to be quite important. Maize was domesticated in Mexico and did not become an important crop in Ohio until about AD90. The first farmers in the region go back 5000 years and they relied on local plants such as sumpweed, goosefoot, may grass and little barley etc. These plants are clearly associated with the mound builders (Adena and Hopewell cultures) – see www.dispatch.com/news/20170820/archaeology-ancient-seeds-pollen-show-ohi…
Seeds and pollen excavated by archaeologists have led to some experimentation (the plants have been grown in gardens to gain insight into how they are domesticated and to explore their potential as food crops in the modern world). These are lost crops – lost to history but rediscovered as a side issue of excavations. The Hopewell people had large fields of these plants growing near their monumental earthworks.
Another interesting story is at www.eurekalert.com/pub_releases/2017-08/uoy-cu082117.php … an agricultural site from 700 years ago in Tanzania, East Africa, had hill terraces and an irrigation system but apparently this did not prevent soil erosion, it has been deduced. It seems the terraces and irrigation canals and walls may even have been designed to capture eroded soil sediments, or mud caused by flooding the irrigation canals. This was in turn used to grow crops as it was rich in nutriants – but on the plain below the hills. It is the largest area of irrigated agriculture in sub-Sahara Africa and significantly it went out of use at the end of the Medieval Warm Period (is there a connection?) What the farmers did, and this is remarkable, was to allow the terraces to flood in order to harvest the flood sediments. These traps were possibly a more important growing medium than the hillside terraces. It also seems likely this form of farming also occurred in South America, the Middle East, and India, largely unrecognised by western scientists until now.
Finally, at https://phys.org/print422244827.html … we have a little history of citrus fruit, introduced to European Mediterranean countries in the Roman era (where they were a luxury item). Citrus are not native to the Mediterranean and originate in SE Asia. Modern oranges and lemons are a product that arrived in the medieval period and presumably a result of trade between Arabs and India etc.