To the early Druid priests of Gaul and Britain, the oak tree held great significance in their rituals and was considered sacred. Likewise mistletoe, which can grow on the oak, also had an important role in their religion. According to a Roman chronicler ‘Pliny the Elder’ writing in the 1st century AD, it was believed that when mistletoe fell from an oak, it was a sign that the tree had been selected by their god.
Pliny states that on the 6th day of the moon, Druid priests dressed in white robes would prepare a banquet beneath the tree and bring up to it two white bulls. A priest would then climb the tree and cut down a branch of mistletoe with a golden sickle. The white bulls would be sacrificed while the attendants prayed to a god; the mistletoe was then given to livestock in a drink which, it was believed, was an antidote to all poisons and would make any barren animal fertile.
Ok now idea time
Make mistletoe grow on oak(wiki dont say it do so i assume oak don't got em), and rarely drop maybe a white mistletoe leaf that when feed to male animal it will breed faster and after it drops for 12 hours or something around that oak tree small boost to fep lol