Two wine festivals were celebrated each year by the ancient Romans. One, April 23 was the urban Roman wine festival,Vinalia urbana, at which occasion wine casks were first opened and tasted, with a libation poured to Jupiter. Not just Rome, but all of Latium celebrated the 2nd wine festival, the Vinalia rustica on August 19, when the flamen dialis offered lambs to Jupiter and then opened the vintage for drinking.
It was originally a rustic Latin harvest festival, celebrating the grape harvest, vegetable growth and fertility. At the Roman Vinalia Rustica, kitchen gardens and market-gardens, and presumably vineyards were dedicated to Venus Obsequens, the oldest known form of Venus. In Roman mythology, it marked the fulfillment of a vow by the ancient Latin allies of Rome's legendary ancestor Aeneas, who promised all wine of the next sacred vintage to Jupiter, in return for victory against the Etruscan tyrant Mezentius. The defeat of the Etruscan King Mezentius, who was, according to Virgil, a “despiser of the gods”, by Aeneas, son of Venus, marks a Roman wine festival that is, interestingly enough, not connected with the Wine God Bacchus.
Opinions of antique authors differed why, besides Aeneas alleged vow, Jupiter was present. The father of the gods appreciated a good drop, like the other gods and goddesses, but it was his role as weather deity that assured a good vintage and wine was regarded as a kingly drink anyway. Thus, on August 19th, a priest of Jupiter picked the first bunch of grapes, blessed the first pressing of it, like the blessing of the first wine that is still celebrated in some Catholic regions today, and offered an “agna”, a female lamb as sacrifice.
Today sacrifices are symbolic gestures. To honor the old ways and show thanks to the gods for the grape harvest, place an image or replica lamb on your altar with grapes and other offerings that correlate with Jupiter, and Bacchus. Light white, purple or burgundy candles. Say a prayer of thanks to the gods. Place a glass of wine at the altar for the father of gods. Drink and be merry, it is a time to celebrate the gift of wine from the gods.