Those who serve good wine don’t need a branch (to advertise)
Il buon vino non ha bisogno di frasca”: an expression much in the same spirit as ‘empty vessels make the most noise’, it proclaims that people who are good at something, are often modest. The saying comes from the tradition of displaying the branch of an oak tree over the doorstep to advertise the fact an inn or osteria served wine.
Of course, if an establishment has a good reputation for its wine, then they will probably already have a loyal clientelle and won’t need to advertise, hence the saying. You’ll still see branches over the doorways of some inns in Italy. But know you know it doesn’t necessarily mean the wine is any good.