Little remains today of the Leonardo’s decorative paintings in a suite of rooms in the north-east tower of the Castello Sforzesco. Although nothing survives of the paintings of the Sala Negra, in the Sala delle Asse (“Room of the wooden panels”) fragments of trees are visibly portrayed on the upper sections of the lateral walls. Leonardo worked on this mural with his assistants.

The branches of the trees are interwoven with golden braids to form a dense canopy that stretches across the ceiling and around the arms of Ludovico Sforza and Beatrice d’Este positioned in the centre. Other tablets on the ceiling with inscriptions refer to the marriage of Ludovico’s niece to the Emperor Maximilian in 1493, and to the Sforza’s claim to the Dukedom of Milan after the death of Filippo Maria Visconti, as proclaimed by Maximilian in 1495. A third tablet proclaims Ludovico’s victory over the French at the Battle of Fornovo, and his journey to Germany to cement an anti-French alliance with Maximilian in 1496.

The trees appear to be mulberry trees and as such are a reference to Ludovico Sforza, who was known as “il Moro”. Surviving documents thought to relate to the decoration of the rooms imply a completion date of 1498 for the work.

The painting was hidden beneath a coat of whitewash until the 19th century and restored in 1901-02, when it was extensively repainted.

A more recent restoration project carried out in the 1950s revealed monochrome under-paintings on the lower section of the wall, where rocks and roots begin some two metres above the floor.

The handling of the underpainting suggests that it is not the work of Leonardo, but undoubtedly it is his conception. It seems likely that he was responsible for the design of the room’s decoration, and executed parts of the painting himself.