The citrus route revealed: from Southeast Asia into the Mediterranean.
Today, citrus orchards are a major component of the Mediterranean landscape and one of the most important cultivated fruits in the region; however, citrus is not native to the Mediterranean Basin, but originated in Southeast Asia. Here, the route of the spread and diversification of citrus is traced through the use of reliable historical information (ancient texts, art, and artifacts such as wall paintings and coins) and archaeobotanical remains such as fossil pollen grains, charcoals, seeds, and other fruit remains. These botanical remains are evaluated for their reliability (in terms of identification, archaeological context, and dating) and possible interpretations. Citrus medica (citron) was the first citrus to spread west, apparently through Persia and the Southern Levant (remains were found in a Persian royal garden near Jerusalem dated to the fifth and fourth centuries BC) and then to the western Mediterranean (early Roman period, ∼third and second centuries BC). In the latter region, seeds and pollen remains of citron were found in gardens owned by the affluent in the Vesuvius area and Rome. The earliest lemon (C. limon) botanical remains were found in the Forum Romanum (Rome) and are dated to the late first century BC/early first century AD. It seems, therefore, that lemon was the second citrus species introduced to the Mediterranean. The contexts of the botanical remains, in relation to elite gardens, show that in antiquity, both citrus and lemon were products representing high social status. Sour orange (C. aurantium), lime (C. aurantifolia), and pummelo (C. maxima) did not reach the Mediterranean until the 10th century AD, after the Islamic conquest. Sweet orange (C. sinesis) was introduced during the second half of the 15th century AD, probably via the trade route established by the Genoese, and later (16th century AD) by the Portuguese. The mandarin (C. reticulata) reached the Mediterranean only in the early 19th century. While citron and lemon arrived in the Mediterranean as elite products, all other citrus fruit most probably spread for economic reasons.