Virescit is latin and it means "rinverdisce", something like "It grows green, it grows up again".
Here's what I found googling:
It comes from a latin expression, quoted by Nietzsche: "increscunt animi, virescit volnere virtus" (gli animi prendono vigore, il valore rinverdisce dalla ferita) = Free translation: Souls get strong, bravery turns green again thanks to the wounds.
Before the final battle, ancients used to cry this out loud.
"Viresco, is, virui, ere" is a Latin verb which means "to revive" (or literally "to grow green again"). Most oldest Italian footbal team adopted a Latin locution in their motto or name, just think of "Juventus" which is Latin for "youth". This case "virescit" is a 3rd singular person and means "(which) revives"