Ritual of oak and mistletoe

The druids – that is what they call their magicians – hold nothing more sacred than the mistletoe and a tree on which it is growing, provided it is a hard-timbered oak [robur][4][5].... Mistletoe is rare and when found it is gathered with great ceremony, and particularly on the sixth day of the moon.... Hailing the moon in a native word that means 'healing all things,' they prepare a ritual sacrifice and banquet beneath a tree and bring up two white bulls, whose horns are bound for the first time on this occasion.

[1][6]While Pliny does not indicate the source on which he based this account, French archaeologist Jean-Louis Brunaux (fr) has argued for Posidonius of Rhodes, a polymath who flourished in the 1st century BC.

[7] Miranda Aldhouse-Green has argued that, although Pliny is the only authority to mention this ceremony, the main elements of his account are all features of Celtic religion that are confirmed elsewhere; these include oak trees, mistletoe, ritual banqueting, the moon, and bull-sacrifice.

[8] Pliny's account has largely contributed to the popular depiction of druids today, as white-clad wise men performing sacrifices in the forests and equipped with golden sickles.

[3] In the Astérix comics, the druid Getafix, robed in white, is often depicted up in an oak tree cutting mistletoe with a golden sickle.