The Other Side of Yew

By Erin Holden

As an herbalist I’m interested in many aspects of plants – from their use in herbal and conventional medicine, to lore that informs us how those in the past viewed the plant. I knew that Taxol was a cancer drug made from the yew tree, but when a friend mentioned its poisonous aspects, I decided to dig a bit deeper.

Taxol, the well-known cancer treatment, was first isolated and studied in the early 1960s into the late 1970s, and approved as a cancer drug in the early 1990s. Paclitaxel, the common chemical name of Taxol, was initially extracted from the bark of the Pacific yew (Taxus brevifolia). It was quickly realized that extracting enough paclitaxel to meet demand would wipe out this species in short order, so scientists turned to its faster-growing cousin, the European yew (Taxus baccata), as an alternative. A precursor of Taxol is extracted from the leaves of the European yew and then synthesized into the desired drug. Use of the leaves instead of the bark, as well as its fast growth, means the European yew is a more sustainable source of this cancer treatment.

Taxus baccata by Maigheach-gheal in the Church of St. Mary and All Saints in Great BritainThis all sounds well and good, but if we look at the history of yew, we see that it didn’t always have the best reputation – quite the opposite. Whereas Taxol belongs to a chemical group called taxanes, another group, the taxines, is quite deadly. These toxic compounds are found in every part of all Taxus species, in varying amounts, except for the red, fleshy aril. When ingested, taxines act directly on the heart and inhibit its ability to pump properly, causing a drastic drop in blood pressure, arrhythmias, and death. There is no treatment for yew poisoning, and supportive care is not always successful in saving a patient. A brief peek into the medical literature shows that yew has been used in many suicide attempts, both successful and non-fatal. Even as far back as 53 B.C., Julius Caesar recounts how a king of Eburones, Cativolcus, took his own life by drinking the juice of the yew. This deadly aspect of yew, as well as its evergreen nature, likely contributed to yew being associated with death and immortality in both Druidic and Christian cultures.

Church_of_St_Mary_and_St_Christopher,_Panfield_-_churchyard_yew_treesWhile researching, I stumbled upon an interesting “explanation” for how yews became poisonous, written in the 17th century. Since Druids considered yew sacred, many were planted all over England. Their long association with death likely led to cemeteries of new churches being placed near the trees. It was thought that decaying bodies released noxious gases on the south and west sides of a church yard, which then gathered under and were taken up by the yews. Yew roots were thought to “run and suck nourishment” from the dead, whose flesh is “the rankest poison that could be”, and so the trees themselves became poisonous. Because of this association, the church itself was built on the north or north east side of existing trees (https://www.theparisreview.org/blog/2015/10/31/beneath-the-yew-trees-shade/).

I find it fascinating how facts and lore surrounding a plant can mix and have such an impact on various aspects of human activity – from medicine to community planning. And how a life-saving plant can also have a sinister side. Think about it the next time you pass by your ornamental yew. 

Photo Credits: 1) Taxus baccata arils (Frank Vincentz, Wikimedia); 2)Taxus baccata at The Church of St Mary and All Saints in Great Britain (Maigheach-gheal, geograph.org.uk/p/2209844); 3)Line of yew trees in the churchyard of St. Mary and St. Christopher’s Church, Painfield, Essex, England (Image © Acabashi; Creative Commons CC-BY-SA 4.0; Source: Wikimedia Commons)

 Resources:

Grobosch, T. et al. (2013). Eight cases of fatal and non-fatal poisoning with Taxus baccataForensic Science International, vol. 227, issues 1-3, pgs 118-126. https://www.sciencedirect.com/science/article/pii/S0379073812005324?via%3Dihub

Laqueur, T. W. (2015). Beneath the yew tree’s shade. The Paris Review. https://www.theparisreview.org/blog/2015/10/31/beneath-the-yew-trees-shade/; Accessed 2/22/2021. 

Lee, M.R. (1998); The yew tree (Taxus baccata) in mythology and medicine. Proc. R. Coll. Physicians Edinb. vol. 28: 569-575;  https://www.rcpe.ac.uk/sites/default/files/vol28_4.1_12.pdf

National Cancer Institute; Success Story: Taxol® (NSC 125973) https://dtp.cancer.gov/timeline/flash/success_stories/S2_Taxol.htm; Accessed Jan 22, 2021.

Rickard, J. (26 March 2009); Cativolcus, king of the Eburones, d. 53 B.C.  http://www.historyofwar.org/articles/people_cativolcus.html; Accessed 1/22/2021.

Medicinal Disclaimer: It is the policy of The Herb Society of America, Inc. not to advise or recommend herbs for medicinal or health use. This information is intended for educational purposes only and should not be considered as a recommendation or an endorsement of any particular medical or health treatment. Please consult a health care provider before pursuing any herbal treatments.


Erin is the gardener for the National Herb Garden at the U.S. National Arboretum in Washington, D.C. She is a member of the American Herbalists Guild, United Plant Savers, and a member-at-large of the Herb Society of America.

HSA Webinar: Hamlet’s Poison: The Mystery of Hebanon & Shakespeare’s Other Deadly Plants

By Jen Munson, HSA Education Chair

‘There’s rosemary, that’s for remembrance; pray, love, remember: and there is pansies. that’s for thoughts.’ (Hamlet 4.5.248)

William Shakespeare’s poetic plays are filled with dramatic imagery and references to plants, herbs, trees, vegetables, and other botanicals. Shakespeare’s awareness of the botanical world was near the level of herbalists of that period, and the use of plants throughout his plays is done with unparalleled sophistication. They are used to enhance ideas and describe characters, as well as for metaphors. For example, Hamlet describes the state of Denmark as “…an unweeded garden / That grows to seed; things rank and gross in nature” (Hamlet 1.22.134-136). 

Plants are used for evil doings and central plot development. They are transformed into potions that are  lust invoking, (Viola tricolor in Midsummer Nights Dream), sleep inducing (Atropa belladonna in Romeo and Juliet), and as poisons for dipping swords and arrows (Hyoscyamus niger in Hamlet). As All Hallows’ Eve approaches, what better time to explore the dark side of botanicals by learning about the many plants cited by Shakespeare. 

Join HSA on October 22nd at 1pm EDT for Hamlet’s Poison: The Mystery of Hebanon & Shakespeare’s Other Deadly Plants, with guest speaker and author Gerit Quealy. During this program Gerit Quealy will take a Law & Order approach to Shakespeare’s poison plants, including what killed Hamlet’s father. The symptoms of the various specimens will be examined, along with the use of forensic evidence, to catch the conscience of the king! Our webinars are free to members and $5.00 for guests. Visit  https://www.herbsociety.org/hsa-learn/hsa-webinars or click here to sign up.


Gerit Quealy is an author, actor, and journalist. Her 2017 publication, Botanical Shakespeare (Harper Design/HarperCollins), reveals Shakespeare’s keen awareness of botany alongside his ability to catapult nature into the land of emotion and metaphor, creating some of the world’s most unforgettable passages. The over 170 flowers, fruits, grains, grasses, trees, herbs, seeds, and vegetables that are named in Shakespeare’s poems and plays, alongside all the lines in which they appear, are highlighted in this unique book. As a journalist, she has covered everything from lipstick to Shakespeare, with pieces ranging from dollhouses to birdhouses to beauty, brownies, and brides in outlets including The New York Times, Country Living, Woman’s Day, and Modern Bride, to name a few.

A Bit about Bitters, Part I

By Erin Holden

From grapefruit to coffee to arugula – lots of plants are bitter. And while some people will cross the street to avoid a bitter veggie, others can’t seem to get enough. Why is this? Join me on a two part journey as I delve into the science and use of one of nature’s most divisive flavors.

The What: How do you define a bitter? If you’re a chemist, they’re structurally unrelated compounds that, well, taste bitter. If you’re an herbalist, bitters are plants that are used for their therapeutic effect on the digestive system. And if you’re a bartender, bitters are aromatic flavoring agents made from various plant parts to enhance the taste of a drink. Based on these definitions it’s easy to see that bitters fulfill many roles in our lives. But why can we taste bitter to begin with?

The Why:Rat poison The main reason plants create bitter compounds boils down to one simple thing: defense. Since plants can’t run and hide from predators, they devised their own chemical defense system – the first instance of chemical warfare, you could say. When an insect bites into, say, a broccoli plant, it gets a mouthful of glucosinolates, sulfur containing compounds that are toxic to insects and rodents, and gross to some people. Plants see us as essentially giant rodents that want to eat them, and create a wide variety of nasty tasting compounds to deter us from doing so. In turn, since some of these compounds not only taste bad but can also kill humans, we evolved taste receptors to detect them, therefore potentially skirting death.

The Where: So, where exactly do we have these taste receptors? I’m sure many of you learned the “flavor map” of the tongue in school, like I did, which outlines where we can detect sweet, sour, salty, and bitter (poor umami got left out on that one). Well I’m here to tell you, that map is bunk! It’s based on the misinterpretation of a graph from 1942, that plotted out areas of relative sensitivity of the tongue to the various flavors. Later on, low areas of sensitivity were mistakenly interpreted as having no sensitivity, leading to the incorrect map we’re all familiar with today. All flavors can be detected across the whole tongue, the back of the roof of the mouth, and the epiglottis. Other research has suggested that while areas of the tongue do show varying levels of sensitivity to the five known flavors, these differences are not significant (Wanjek, 2006).

Taste_buds

Photo Credit: MesserWoland

Having taste receptors on the tongue is no surprise, but you may be surprised to learn bitter receptors have also been found in the brains, airways, gastrointestinal tract, testes, and pancreas of various mammals (including humans). This leads back to WHY? The prevailing hypotheses boil down to the same thing – protection. If our airways are full of bacteria that are producing bitter compounds, our cough response is triggered, so we cough up and expel the offending invader. If an ingested bitter toxin makes its way to our guts, it’ll essentially trip the “abandon ship” alarm, causing our body to purge itself of the potential poison in unpleasant ways.

I’ll stop there with that thought. Keep an eye out for the follow-up, where I’ll talk about the historical uses of bitters, their role in herbal medicine, and mention some specific bitter herbs.

Wanjek, C. 2006. The tongue map: Tasteless myth debunked. Live Science. From Livescience.com. Accessed January 31, 2019. Available from https://www.livescience.com/7113-tongue-map-tasteless-myth-debunked.html on 1/31/2019

Medicinal Disclaimer: It is the policy of The Herb Society of America, Inc. not to advise or recommend herbs for medicinal or health use. This information is intended for educational purposes only and should not be considered as a recommendation or an endorsement of any particular medical or health treatment. Please consult a health care provider before pursuing any herbal treatments.


Erin Holden is the gardener for the National Bonsai and Penjing Museum at the U.S. National Arboretum in Washington, D.C. She is a member of the American Herbalists Guild, United Plant Savers, and a member-at-large of the Herb Society of America.

 

 

 

Do you consider poisonous plants to be herbs?

By Paris Wolfe, Blogmaster, The Herb Society of America

skull_and_crossbones_clip_art_9050Most of us grow herbs to treat the senses with beauty, aroma or taste. We may tap their chemical properties to treat internal or external illness. Whatever the case, we likely use plant material to enhance life.

That wasn’t (isn’t?)  always the case. The poison garden had a special place in history as a way to off the enemy. In a demonstration garden, Blarney Castle in Ireland grows plants that are so dangerous and toxic that they may be kept in “cages.” Included in the collection are wolfsbane, mandrake, ricin, opium and cannabis. Brave visitors can read labels with information about their toxicity and traditional and modern uses.

Ironically, some plants now known to be toxic were once used widely as herbal remedies. And, perhaps some of their components still are.

Recognizing a fascination with these “magical” plants, the Cleveland Museum of Natural History is in the final weeks of “The Power of Poison.” This exhibition, which ends July 24, 2016, includes plant toxins’ roles in nature and human history as weapon, defense and lifesaving healer.

People have long put poison to work—using it in hunting and fishing, making dyes and pigments, developing pesticides and herbicides, and even as a path to altered consciousness. And breakthrough medical applications continue to elevate that “magic.”

poison hemlock

Poisonous Hemlock

In the exhibit, visitors learn about the powers of belladonna, hemlock, monkshood, and rhododendron.  Hemlock (not the tree), for example, contains a toxin that was used to sedate and to treat spasms, but can cause death; the ancient Greek philosopher Socrates was executed by being forced to drink hemlock brew.

Children (and adults) may be titillated with tales of the manchineel tree, the most poisonous tree in the world. The manchineel’s milky white sap is so dangerous that even a drop can cause skin irritation or burns. The sap is so caustic that even the rain drops coming from the branches can cause burns.

What do you think … are poisonous plants considered herbs?