The arboreal decoration remained hidden beneath up to 13 layers of paint until 1893, when renovations to the castle revealed traces of frescoes.
In 1901, amid much criticism, the mural was heavily restored.
Only in 1954, the paint applied during the disastrous restoration was finally removed. But damage to Leonardo's work remained.
"The mural is covered by a thick layer of grime. However, our cleaning tests indicate that it can be easily removed. Leonardo's paint won't be damaged in the procedure," the restorers wrote.
Meanwhile, archival research also revealed the room's original name.
It was called "Camera dei Moroni" -- a clear allusion to Ludovico il Moro.
Indeed Leonardo's decoration is filled with punning allusions. The mulberry, or Morus tree, refers to the Duke’s well known nickname, Il Moro, the Moor. The tree is also a symbol for the Milanese silk industry - mulberries were cultivated in the region as food for the silkworm.
"This restoration is extremely important to fully understand Leonardo’s work," Milan culture councillor Filippo Del Corno said. "The project will last two years, ending just in time for the Milan's Expo 2015," he added.