Purple petunias, white leadworts and medicinal vervain have been planted in the ruins of courtyards and shrines where scribes of the time described luxurious gardens created in imitation of the ancient Greeks.
"The Palatine was not only about architecture. It was a game of colours -- frescoes, fountains and flowers. It was nature penetrating into the city," said Maria Rosaria Barbero, the head of Rome's archaeological department.
"We wanted to give the Palatine back its colours," she said, looking at a bed of petunias surrounded by terracotta-red ruins in what was once a vast inner courtyard of the Flavian Palace built by the Emperor Domitian in 92 AD.
"The emperors wanted their Palatine residences to be decorated with splendid gardens that with their magnificence could help legitimise the sacred nature of their authoritarian power," a statement said.
The additions include a partial reconstruction of the 16th century Orti Farnesiani, Italy's first botanical garden, which contained plant species discovered in the Americas just a few decades before by Christopher Columbus.
Organisers said they could not, however, also recreate the many fountains that dotted the hill, which overlooks the Colosseum and the Roman Forum, because of the difficulty of pumping up such large amounts of water.
The Palatine Hill was the most luxurious residential quarter of ancient Rome and its palaces appear in literature as far back as the fourth century BC.
It was inhabited at various times by the philosopher Cicero and the emperors Nero and Augustus. The word "palace" originates from "Palatine".