My research of the herbal section of the Voynich Manuscript let me to believe that some of the drawings were influenced by the Pseudo-Apuleius tradition. Judging by the surviving manuscripts Pseudo-Apuleius was fashionable between 10th and 12th century. The revival in interest of this herbal tradition in 15th century was in 1481 when Johannes Lingamine, personal physician of Pope Sixtus IV (the Sistine Chapel is named after him) printed Herbarium Apuleii Platonici. According to Lingamine the book is based on old manuscript he found at Monte Cassino which was worth printing.
So the circle of frienemies fighting at Fornovo had personal connection to the Pseudo Apueius herbal tradition.
Of course, there are many visual connections made between the Voynich Manuscript and other traditions - the main suspects are alchemy herbals and classical Dioscorides.
Also, Rene Zandbergen proposed several very interesting possible ids for the VMs plants based on similarities with the 14th century French manuscript Manfredus de Monte Imperiali (BNF Latin 6823, visit here ). In 1426 the manuscript appears in the inventory of the Visconti library. My favorite among this ids is the oak/ivy combination on fol. 35v so I will put it as placeholder for that page in my list.