In this paper, we present a detailed record of the plant remains recovered on the palaeo-seafloors of Neapolis harbour, spanning ≈700 years, between the 2nd century BC and the 5th century AD, thus intersecting the entire Roman Imperial Age. The site preserved many cultivated or cultivable plant remains, especially from food related trees. This particular feature provided the opportunity to reconstruct the puzzling history of planting them and the Roman economy, especially with respect to food production, the market and to dietary habits. The evidence suggests that Prunus persica, Castanea sativa, Juglans regia and Pinus pinea were locally grown all along the investigated period, testifying for a well advanced arboriculture. A broad presence of P. pinea cones could be related to their large use as stoppers for amphorae which probably was among the driving force for planting it actually influencing its original range. The seafarers had extensive access to dry fruit such as walnut, hazelnut and chestnut that for its imperishable nature and the high energy density, would probably have been part of the food-stocks of the galleys. Chestnut consumption, attested throughout the entire period in the harbour, represents the first strong archaeobotanical evidence of chestnut as food in the Western Mediterranean in Roman time. This evidence shed light on the cultural-social significance of these fruits that was probably eaten mainly or almost exclusively by low social classes. The exceptional find of Hyphaene thebaica for the first time outside its native range is also reported.