Mistletoe

Mistletoe was a plant found on Earth.

It was believed that the Host — a werewolf — either was allergic to the substance or was conditioned to believe it was. Proof of this appeared in the wolf's reactions to the mistletoe. Firstly, the monks wore mistletoe around their necks so that they were not attacked. Secondly, walls varnished with oil of mistletoe kept the wolf out of the library. Lastly, the wolf was pushed away when Lady Isobel threw mistletoe broth at it. (TV: Tooth and Claw) "Mistletoe had always been a plant of mystery. There had been a legend in the Middle Ages that the cross on Calvary had been made of mistletoe. It had been cursed never again to grow from the ground, but to shrink and only grow from other trees. It was later brought into homes in winter with other evergreens as a pagan offering to pray for the spring to come, and the concepts of rebirth had converted it into a kissing-bough. Mistletoe "stole time" in anagrammatic form — very suitable for the lost Wise Man."

- The Fourth Doctor's thoughts

According to the Eighth Doctor, "You get mistletoe at Christmas." (PROSE: Time Zero)

Barbara Wright kissed Ian Chesterton under the mistletoe on Christmas 2004. (PROSE: Every Day)

When they were ten years old, a boy tried to snog Caroline Darnell under some mistletoe he'd brought to school. (PROSE: The Sleep of Reason)

Jasmine Deering traditionally had drunks try to kiss her under the mistletoe every Christmas; one attempted to do so with plastic mistletoe, which she said didn't "count". (PROSE: Christmas in Toronto)