Science in School: Why We Kiss Under the Mistletoe


Aarna Pal-Yadav, Columnist

Everyone knows the Christmas tradition of kissing under the mistletoe; it is nothing new. The connection between mistletoe and kissing dates back to Norse mythology. Son of all-father Odin and the goddess of spring, Frigg, Baldur is the unrecognized brother of beloved Thor and infamous Loki. The legend says that Baldur was prophesied to die and Frigg journeyed to all the animals and all the plants of the world to make them promise to protect her son. But Frigg forgot one plant: the mistletoe. Knowing this, Loki made an arrow from mistletoe and shot Baldur, instantly killing him. The gods were able to bring Baldur back from Valhalla and Frigg was overjoyed. She promised to kiss everyone who walked beneath the mistletoe, making it a Norse symbol of love. 

Before the Norse, the Greeks used mistletoe as a cure-all for everything from cramps to poison! When the Celtics came around, they saw mistletoe as a symbol of liveliness, for it bloomed even in the coldest of winters. Men, women, and cattle were all fed the mistletoe plant to improve fertility. Mistletoe became associated with Christmas during the 1800s. Originally, servants in England believed men could kiss any woman passing under the mistletoe and it would bring misfortune to the woman if she refused. It then spread to the middle class: a couple would remove one mistletoe berry for every kiss, and once all the berries were gone, it was time to get back to work. 

While the stories behind mistletoe are truly touching, the plant is actually a hemiparasite, meaning it uses photosynthesis to gain some nutrients and its host for the rest. In nature, this lovely little parasite situates itself in tree bark where it sends roots to steal the tree’s water and nutrients. An adult tree can survive with a little mistletoe, but if there’s too much, it will suck the life out of it. Nevertheless, mistletoe plays an important role in the ecosystem as birds eat the berries and use the plant to make nests. The trees it kills also become standing posts for raptors. 

Though mistletoe is associated with kissing, keep the pretty pink berries away from your lips— some species are highly poisonous! Most adults can consume a mistletoe berry and walk away unscathed, young children and pets should be extra cautious. All mistletoe species are part of the Viscum genus and contain the toxic alkaloid tyramine, which can cause blurred vision, nausea, abdominal pain, diarrhea, blood pressure changes, and even death. So don’t let your holiday be spoiled by mistletoe poison— these bright red berries are not the tasty treat they appear to be. 

While humans can’t eat mistletoe, birds love it! Mistletoe spreads when birds eat the berries and excrete the seeds in their roosts. The Anglo-Saxons realized that mistletoe seemed to sprout from bird feces on branches so they called it “misteltan,” with ‘mistel’ meaning dung and ‘tan’ meaning twig. This eventually turned into “mistletoe.” 

So, mistletoe may be a parasite, it may be poisonous, and it may be named after bird dung, but don’t let that ruin your holiday! Mistletoe embodies the spirit of love during the holidays.