Mistletoes get an interesting and sort of bad rep. They are only really thought about during the holidays (unless by botanists) and many have heard that they are super toxic and kill trees they live on. And yet you’re supposed to smooch under them. Why? Wouldn’t you NOT want to apply your mouth to a person when they are under a toxic plant, just in case some falls on their face right then? Well let’s pick all this apart. If you did see mommy kissing daddy underneath the mistletoe last night, or maybe a while ago, then they may have been trying to get a little sibling under the next Christmas tree.
Mistleotoe is multifaceted.
They have interesting chemistry, botanical physiology, and even mythology.
First the MYTH:
I am surprised that many people don’t know the ‘why’ of kissing under mistletoe. Why is this a tradition? Well it’s basically for fertility. Ew.
Because mistletoe has such an unusual biology, it crafted tales from the people who came across it. Mistletoe is found in many areas of the globe and a lot of peoples have connected to it through history.
It is likely the very fact that mistletoe remains green and productive through the depths of barren winter that it was associated with fertility and new life.
Mistletoe was considered magical and lucky by the Druids. These Celts were possibly the first European peoples to connect with mistletoe in a spiritual way. A rare species grew on the Druidic sacred oak trees and was of course considered to have special powers. It was collected during the equinox solstices, including around what we now know as Christmas time.
The ancient Greeks were the ones to start the tradition of kissing under it, as it was used in festivals and marriage ceremonies, because of its association for them with both peace and fertility. The historian Pliny recorded that the mistletoe plant was most sacred to the Celts of Gaul because it grew upon their most sacred tree of oak. Thus it must be sent from heaven, to be growing upon such sacred branches and these trees were specially chosen by the gods. These Celts believed a concoction of mistletoe would make barren cattle give birth, and cure any poisoning, based on their myth of Fridda and her son.
In Nordic mythos, the goddess of love Fridda (aka Freya) revived her son underneath mistletoe. He was shot with a poisoned arrow, and Fridda decreed all beneath a mistletoe shall then be protected from death and even deserve a kiss. I guess that's a perk from a love goddess. The Greeks started the smooching but the Celts of northern Europe brought it to modern western tradition. The early Christians of Europe absorbed the Norse tradition of kissing with hopes for fertility and peace and cure for ailments underneath a mistletoe sprig.
This expanded into secular tradition. I have thoughts as to why. If you follow the official etiquette of the early 1800s, a gentleman beneath the holiday mistletoe should pluck a white berry while kissing a fair maiden (on the cheek guys… you rascals!) and he may get a kiss for each berry. So the gents at the end of that party evening are fresh out of berries.
Ainoa people of Japan had very similar beliefs of mistletoe as a cure and to help women’s fertility. Mistletoe also grows in Africa, where a few similar beliefs are found among peoples such as the Walos of the previously named Senegambia region (or so noted Sir Frazer). There is no great curiosity why ancient people would be so enchanted by a lush green plant, still alive through winters and alighting only on tree branches, with no visible roots, flourishing solely in the air, never touching the life-giving earth. They are a botanical marvel.
And in fact it has some recently found medical links to fertility aiding in recovery after miscarriages (for bleeding) and yet can also cause them (though in rats) during early stages (Unoh et al.2005). Other uses for mistletoe include emergency food by Native peoples, medicinal treatments in various teas, applied to warts, stomach issues, and relaxing muscles during birth (by Zuni of New Mexico area).
The Botany:
What IS a mistletoe plant? You may have seen them hung from a doorway or ceiling during the winter holidays, but did you note any distinct characteristics? Busy otherwise perhaps. We've already mentioned they are evergreen. They also have small non-showy green flowers which produce often white or pale berries and grow as short woody shrubs straight out of tree branches. They are actually a valuable plant in their native areas because their berries are essential winter food for several bird species. There are many species known as mistletoe, from several genera and all are fairly closely related. They mostly all share thick leathery rounded leaves in opposite pairs, small drab flowers, and pale berries in common. North America has the American mistletoe (Phoradendron leucarpum) on the east side, which hosts on deciduous trees, especially oaks, red maple, and elm in the south. Then there's a big leaf and some dwarf species in the western US and Mexico. Most people are familiar with the European species (Viscum album) which tends to host on apple and junipers. Some species are entirely parasitic (like the dwarf ones in the Arceuthobium genus) without any of their own leaves and feed entirely on the host plant, thus they can actually be deadly to the host plants (mostly conifers). Mistletoes tend to ‘prefer’ some trees but can also host on introduced trees not native to their area. This can be a problem in crop species.
Mistletoes are all related to a very old parasitic tree
Mistletoes are mostly hemiparasitic plants that grow and often feed on a host plant, usually a few specific types, but they don't necessarily need a host for food. Some prefer oaks, some host on a small variety of trees, and some prefer junipers. They all live as epiphytes, established on top of a larger plant (aka trees), similar to some orchids and ferns. Those without any green parts are lacking food-making chlorophyll, thus entirely dependent on the host for food (fully parasitic). Unlike often misrepresented, most mistletoes (and most parasites) do not bring significant harm to the host. That's not a good evolutionary strategy. Mistletoes as a group are so diverse, they even belong to several families, hinting at interesting evolution, yet many still very recognizable as mistletoe.
They tend to be easiest to spot in winter especially on deciduous trees because they are still green and will stick out like a green bushy thumb among otherwise barren branches of a deciduous tree, plus a bit lower down on a large branch than where the other leaves would be. The famously ancient bristlecone pines (see previous post) are in fact the primary host of a dwarf mistletoe (Arceuthobium cyanocarpum) and essential to its survival. And there is a mistletoe (Phragmanthera incana) in Nigeria that grows on Theobroma cacao, which chocoholics may recognize as the cocoa tree which provides us with chocolate. This I am less ok with- anything reducing the possible productivity of cocoa pods.
There is a very unique species that has lovely long frilly clusters of red flowers that emerge straight out of the thick skin of cacti (only 2 species of the tall thin columnar types), native to Chile- Tristerix aphyllus. Fascinating! It would be hard to kiss someone under it, but maybe under the right cactus with a lateral growing branch. Kiss carefully, like porcupines do.
Mistletoes are all related to the very old species of parasitic tree, sandlewood. The same we get incense from. Sandlewoods use their specially adapted vampire-like roots (haustoria), that is the tool of the parasitic plants' trade, to stab and feed off other trees’ roots. Thousands of years ago, mistletoes split and evolved from these trees that feed on trees, into a smaller shrub that lives within and feeds on trees. Mistletoes had to evolve a tougher haustoria to puncture the tougher bark of a tree branch than their roots, though larger roots can certainly become quite tough and woody as well. Phylogenists (scientists studying the evolutionary relationships of organisms) have tracked the evolution of these shrubby branch-dwellers from their sandlewood ancestors to 5 separate groups- evolving and splitting from their tree ancestor 5 different times, which is why there are so many different genera of mistletoe. Apparently it’s a very successful life strategy. The first step in evolving was likely their berries (fairly similar to the sandlewood's) and being transported into tree tops in the first place. The successful ones were able to tap a haustoria into the branch as their next evolutionary step. And voilà, mistletoes. Well, very simplified.
How DOES a mistletoe seed get up on a high tree branch anyway? Wouldn’t they just fall or wash off to the ground? Well, poop. Literally. Birds can rely heavily on the nutritious (and often sticky) berries in winter, when little else is available. And what do birds do best on trees? Their feces will glue the now berry-free seeds to the tree bark. The Anglo-Saxons named it “mistel tan”, meaning “feces twig”. Not exactly poetic but descriptive. Try that in a pick up line at the next holiday party. “Wanna smooch under the poop-twig there?” Which brings us back to - toxicity.
We've got Chemistry:
European mistletoes have been used medicinally for various ailments like dermatitis, asthma, headaches, infertility (of course), seizures, and rheumatism. It is often prescribed for cancer treatments in Europe, yet still has no substantiated data on that application. And indeed there is some interesting chemistry in this odd-ball plants.
Following today's theme, mistletoes still live up to their legends. Most mistletoes are in fact considered toxic, but they vary in level and probably not all have been assessed. Generally all parts of the plant have some toxicity as well. Mistletoe's toxicity is more commonly known from the European species (Viscum album) thus the American (Phoradendron serotinum) had been assumed toxic by association. Now the American mistletoe is also known to have phoratoxin in all plant parts. European mistletoe also has toxins in all parts of the plant though only a little in the berries, which is how some people can eat them as an emergency food. The toxin is different from American mistletoes though, with viscotoxins and lectins in the European species (Viscum album) and in other Phoradendron species. Viscotoxin express the most harm where our tissues are growing very quickly, like the gastrointestinal tract because they prevent the development of new cells. Hence, some tummy upset from mistletoe ingestion, which has been recorded. Ingestion can also lead to delirium, kidney and liver damage, some central nervous system damage, vomiting, and slow your heart rate (if you consumed a lot). Slowed heart rate is from cardiac depressants in some mistletoes as well (phoratoxins & ligatoxin A, specifically).
But how toxic is it?
Most cases of mistletoe “poisonings” happen, unsurprisingly, during winter holidays and are from children. But the majority of these incidents were just “exposures” with no symptoms or fatalities, even when the plant was purposefully swallowed, thus likely ingesting a larger quantity than those by accident. In 11 cases where young children swallowed between 1 and 5 whole leaves, about 1/3rd of these children had gastrointestinal discomfort. Findings hint that the American species are less toxic than the European's phoratoxin, though still should not be made into a salad. The European species have been known to cause serious poisonings and deaths but that's usually from concentrating a lot of the phoratoxin into a tea. You would have to eat a lot of leaves to cause death, like most toxic plants. Generally, a lot plants cause some irritation, rash, or upset tummies, or can give less obvious issues like straining the organs. We have many as common house plants everyday. Few plants can kill from one nibble.
You may be questioning now- what about poinsettia? Also famously holiday-toxic. Well it’s complicated. Much like mistletoe, toxicity has been exaggerated and very few actually cases of confirmed poisoning have been found and mostly due to a dermal irritation. Poinsettias are in the very commonly toxic Euphorbia genus with their famous white sticky (milky) sap that can cause severe burns from skin exposure. And they also make latex and rubbers. The poinsettia species (Euphorbia pulcherrima – meaning “beautiful” in Latin) has been found to NOT contain the toxic Euphorbia terpene compounds, so it’s pretty much just causing an allergy to the same people who have an allergy to latex. 92% of poinsettia ingestion had no symptoms, of 22,793 cases. Still, I wouldn’t rub it on my face, or make a poinsettia salad.
Feeling safer now for the next year’s holidays? Well don’t worry, there are still terrifying family dinners and in-laws, and evil cousins, and denser-than-lead fruit cakes to keep you on your toes. Under the mistletoe. If you are working on your fertility, that is.
Now *I* feel panicky!
Time to hide in the dark rainy woods to calm down.
References:
https://www.livescience.com/32901-why-we-kiss-under-mistletoe.html
F.B, Unoh & A.E, Eno & Nkanu, Etah & Imoru, Joshua & Ofem, Ofem & J.O, and. (2005). “The Effect of an Aqueous Extract from Viscus album (mistletoe) leaves on the Uterus and Gestation Period in the Rat”. PeCOP Journal of Tropical Medicine and Health, vol 2.
https://www.researchgate.net/publication/233844695_The_Effect_of_an_Aqueous_Extract_from_Viscus_album_mistletoe_leaves_on_the_Uterus_and_Gestation_Period_in_the_Rat_PeCOP_Journal_of_Tropical_Medicine_and_Health_vol_2_no_12_9-19
https://alienplantation.wordpress.com/2012/12/24/students-of-ethnobotany-underneath-the-mistletoe/
https://parasiticplants.siu.edu/Loranthaceae/TristerixAphyllus.html
“The Golden Bough- study in religion and magic” by Sir James Frazer. Dover Publications. 2002
Native America Ethnobotany DB: http://naeb.brit.org/uses/search/?string=Phoradendron+juniperinum+
Zabrina N. Evens, MD and Samuel J. Stellpflug, MD “Holiday Plants with Toxic Misconceptions”. 2012. West J Emerg Med. Dec; 13(6): 538–542. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3555592/
https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/mistletoe