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The mistletoe is an enduring icon of Christmas love, and it’s a time-honored tradition for couples to stand under this Yuletide decorative staple and kiss one another. Far from being just an excuse to lock lips, though, the evergreen plant actually has both an interesting etymology and an important role in the ecosystem.

It’s widely believed that the name was coined after someone noticed it growing out of bird excrement on tree branches. Thus, the old Anglo-Saxon words for dung (“mistel”) and twig (“tan”) were combined, eventually morphing from “misteltan” to “mistletoe” as the centuries passed.

Mistletoes are hemiparasites, meaning that while they do get some of their energy via photosynthesis, they suck the rest out of other plants. This parasitic shrub can latch onto a wide variety of flora, draining and weakening its chosen host. While this may sound like a bad thing, it actually gives this plant an important role to play in nature: Aside from being eaten by birds and other animals, mistletoe-infested trees also serve as nesting sites. In fact, a mistletoe-infested forest can have three times more birds nesting in tree cavities than a forest with none of the plant.

There are over 1,300 known species of mistletoe worldwide, each with different levels of toxicity. (The one we use for Christmas decorations is 𝘝𝘪𝘴𝘤𝘶𝘮 𝘤𝘳𝘶𝘤𝘪𝘢𝘵𝘶𝘮, the red-berry mistletoe.) Any part of the plant, whether leaf, stem, or berry, is poisonous when ingested in solid or liquid form. However, most of the documented cases did not result in severe reactions, and there are hardly any recorded instances of death by mistletoe consumption. It’s also worth noting that mistletoe extract has been used in cancer therapy for decades to stimulate the immune system; however, experts only recommend doing this in well-designed clinical trials, as there’s little proof of it being safe or effective outside of a controlled laboratory setting.

So how did we end up associating this toxic plant with such a joyful holiday? Many historians believe that it’s partly because the plant has traditionally been associated with fertility, and partly because its red berries and brilliant green leaves compelled people to use it for decorating their houses during wintertime.

So remember: Don’t eat any part of this plant if you don’t want to spend the rest of your evening in pain. (Oh, and don’t kiss anyone without their consent, tradition be damned.)

Today’s Science History Milestone: On December 22, 1891, German astrophotographer Max Wolf spotted 323 Brucia asteroid. It was the first asteroid discovered using photography.

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  • https://www.smithsonianmag.com/science-nature/poop-tree-parasite-mistletoe-180967621/
  • https://www.nationalgeographic.com/news/2015/12/151218-mistletoe-christmas-holiday-kissing-parasite-birds-cancer/
  • https://blogs.biomedcentral.com/bugbitten/2015/12/22/mistletoe-parasite/
  • https://www.nytimes.com/2007/12/11/health/11real.html
  • https://medlineplus.gov/ency/article/002883.htm
  • https://www.cancer.gov/about-cancer/treatment/cam/hp/mistletoe-pdq

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Author: Mikael Angelo Francisco

Bitten by the science writing bug, Mikael has years of writing and editorial experience under his belt. As the editor-in-chief of FlipScience, Mikael has sworn to help make science more fun and interesting for geeky readers and casual audiences alike.