Pliny Natural History, Vol. IV (Loeb Latin-English)

It is recorded that the Gauls, confined by the Alps as by an insuperable barrier, found their first motive for overflowing into Italy in the fact that a Gallic citizen from Switzerland named Helico, who had stayed in Rome for his skill as a craftsman, brought back with him dried figs, grapes, and samples of oil and wine. For this reason, it may be forgiven that they sought these things even by war.

6 III. But who would not justly marvel that a tree has been sought from another world merely for the sake of shade? This is the plane tree, which was first brought into the Ionian Sea as far as the island of Diomede for the sake of his tomb. From there it crossed into Sicily and was numbered among the first gifts to Italy; and now it has been carried as far as the country of the Morini, occupying even tributary soil, so that the people must pay tax even for the shade.

7 The elder Dionysius, tyrant of Sicily, transported them to the city of Reggio as a marvel of his house, where a gymnasium was later built. It is found in the authorities that they could not grow to full size and that there were no others in all Italy and Spain.

8 IV. This happened around the time of the capture of the city [Rome]. So much honor has since increased for them that they are nourished by having wine poured on them. It has been found that this is most beneficial to the roots, and we have taught even trees to be wine-bibbers!