Your unease about mistletoe is well founded. Mistletoe berries, for one thing, are poisonous, and some species can kill the trees that host them.

Even worse is the legend that supposedly accounts for our custom of kissing under the mistletoe at Christmas. In the account given by Edgar Nash in the Saturday Evening Post in 1898, the Scandinavian god Baldur told his mother Frigga that he had a premonition of death, whereupon Frigga extracted promises from every animal, vegetable, and mineral that it would not harm her son. She overlooked only the inconsequential mistletoe, a fact that came to the unfortunate attention of Loki, the god of destruction. Loki promptly hustled over to where the other gods, obviously in desperate need of entertainment, were hurling spears and whatnot at Baldur for the fun of seeing them swerve aside without harming him. The pitiless Loki, however, shot an arrow of mistletoe*, which fatally pierced Baldur’s heart. Rather than punish Loki, the gods decided the answer was mistletoe control, and turned the plant over to Frigga to do with as she saw fit, provided it did not touch the ground. (Why it was important that it not touch the ground I do not know, although since it grows on trees mistletoe in fact generally does not touch the ground.) Frigga hung up the mistletoe and, to show she did not bear a grudge, declared that all who passed beneath it should receive a kiss of love and forgiveness rather than, say, a severed aorta. So when somebody smooches a fellow hominid who has strayed beneath the mistletoe, he or she is implicitly saying: be grateful it’s only a kiss, babe, I could have killed you.

The tradition of hanging it in the house goes back to the times of the ancient Druids. It is supposed to possess mystical powers which bring good luck to the household and wards off evil spirits. It was also used as a sign of love and friendship in Norse mythology and that's where the custom of kissing under Mistletoe comes from.

When the first Christians came to Western Europe, some tried to ban the use of Mistletoe as a decoration in Churches, but many still continued to use it! York Minster Church in the UK used to hold a special Mistletoe Service in the winter, where wrong doers in the city of York could come and be pardoned.

The custom of kissing under Mistletoe comes from England. The original custom was that a berry was picked from the sprig of Mistletoe before the person could be kissed and when all the berries had gone, there could be no more kissing!

The name mistletoe comes from two Anglo Saxon words 'Mistel' (which means dung) and 'tan' (which means) twig or stick! So you could translate Mistletoe as 'poo on a stick'!!! Not exactly romantic is it!